Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF 2-HYDROXY-4-METHOXY -BENZALDEHYDE"

Abstract

An improved process for the preparation of 2-hydroxy-4-methoxybenzaldehyde which comprises reacting a phenolic compound, as herein defined, with alkali hydroxide such as KOH or NaOH, in presence of cyclodextrin or its derivative such as herein defined, at a temperature in the range of 50-70° C, adding CHCL3 to the above said reaction mixture over a period in the range of 5 to 1O hrs and further holding the reaction mixture at the same temperature for a period in the range of 4-8hrs, adding methylating agent, such as described herein, in situ and stirring the reaction mixture at a temperature in the range of 30 to 80°C for a period in the range of 1 to 5 hrs and recovering 2-hydroxy-4-methoxybenzaldehyde from resultant by conventional methods as described herein and converting 2, 4-dinydroxybenzaldehyde into monomethyl ether by reacting it with methylating agent in the presence of cyclodextrin or its derivative to give 2-hydroxy -4-methoxybenzaldehyde.

Full Text

This invention relates to a process for the preparation of 2-hydroxy-4-methoxy-benzaldehyde. This invention particularly relates to a process for the preparation of 2-hydroxy-4-methoxy-benzaldehyde from resorcinol, 2,4-dihydroxybenzaidehyde and resorcinol monomethyl ether using β-cyclodextrin (βCD) and its derivatives: βCD epichlorohydrin polymer, heptakis-2,6-dimethyl-β-cyclodextrin-(DMβCD) and hydroxypropyl-β-cyclodextrin-(HPβCD). 2-Hydroxy-4-methoxy-benzaldehyde(4-methoxyresorsaldehyde) is the pleasant aromatic aldehyde present in swallow roots (Decalepis hamiltonii, Wight and Am.) which on steam distillation yields about 0.8% of the compound (Murti,P.B.R and Seshadri, T.R., Proc. Ind. Acad. Sci, ISA, 1941, 221). It is also present to the extent of about 0.225 % in roots of Hemidesmus Indicus (Indian Sarsaparilla) (Murti,P.B.R and Seshadri,T.R., Proc.Ind.Acad.Sci. ISA, 1941, 399- 403) and 0.26% in roots of Tylophora indica (Wealth of India, Indian Raw Materials and Industrial Products, Vol. X, Sp-W, Publications and Information Directorate,CSIR, New Delhi 110 012, 1976, p. 399.) another member of the family Asclepiadaceae besides Decalepis. The interest in this compound is mainly due to its flavour note, strongly resembling vanillin, which is obtained both synthetically and naturally (from the cured pods of Vanilla planifolia). It has been found that the compound can also be used as an antimicrobial agent 'NY Phadhe, A S Gholap, KRamachandran and G. Subbalakshmi, J.Fd.Sci.TEch. 1994, 31,472-475). Cyclodextrins are known to form inclusion compounds with a wide variety of organic molecules. Cyclodextrins also mimic enzymes whereby they have been shown to catalyse a wide variety of organic reactions. When substrates included inside cyclodextrin cavity are subjected to reactions by using suitable reagents, regiospecific products evolve due to selective direction of reagents to specific exposed regions of the included substrates (Maheswaran, M.M. and Divakar, S., J. Sci. Ind. Res., 53, 1994, 924) . This property is made use of in the production of 2-hydroxy-4-methoxybenzaldehyde. Under the best conditions employed, the yield of salicylaldehyde and p-hydroxybenzaldehyde from phenol in Reimer-Tiemann reaction was reported to be 80% based on reacted phenol but only 50% relative to chloroform (US patent , 3,365, 500, 1964 to DOW Chemical Co.) the ratio of salicylaldehyde to p-hydroxybenzaldehyde being 65:35 in the presence of solvent (Fiege, H, Wedemeyer, K, Bauer, K. A., Krempel, A. and Molleken, R. G. in Fragrance and Flavour substances, edited by Rodney croteau ,D and PS Verlag, 3017; Pattensen, W. Germany, 1980, pp.63; Satchell, D. P. N. and Satchell, R. S-. in The Chemistry of the carbonyl group, edited by Saul Patai, Interscience Publishers, John-Wiley and Sons, Chichester, 1960, pp.293). In comparison with the reaction with phenol in the presence of cyclodextrins which exhibited about 96-100 %(Komiyama, M. and Hirai , H. Bull. Chem. Soc Japan. 54, 1981, 715) selectivity with respect to the para product, the reaction with catechol and guaiacol yielded about 82-86% of the para product (of the total aldehydes produced) selectively in the presence of βCD and its water insoluble polymer (Divakar, S., Maheswaran, M. M. and Narayan, M. S., Ind. J. Chem., 31B. 1992, 543). Resorcinol embedded in β-cyclodextrin, when subjected to Reimer-Tiemann reaction, gave exclusively 2,4-dihydroxybenzaldehyde (-100% selectivity) in contrast to the control reaction which yielded two products. 2,4-dihydroxybenzaldehyde (24%) and a dialdehyde(40% - Komiyama, M. and Hirai, H., Makromol. Chem. Rapid Commn.,2, 1981, 707) Earlier it has been shown that vanillin (4-hydroxy-3- methoxybenzaldehyde) and protocatechuic aldehyde (3,4- dihydroxybenzaldehyde) are included inside βCD cavity with the phenolic hydroxyl and OCHs end inside and the aldehyde end outside the cavity, based on detailed ultraviolet, NMR (Nuclear Magnetic Resonance), circular dichroic spectroscopic and potentiometric studies (Divakar, S., J. Agri. Food Chemistry, 38. 1990, 940; Maheswaran, M. M. and Divakar, S., J. Incln Phenom., 1996). Although it is related to vanillin in structure and flavour note, this compound is not produced in commercial quantities like vanillin. Hence, this compound can be prepared by the procedures employed for that of vanillin. This compound can be produced from either resorcinol or resorcinol monomethyl ether. The procedures for the preparation of vanillin yields a mixture of compounds and side products. Even those that give rise to greater selectivity in case of vanillin, involve difficult work up procedures and environmental pollution. Hence, the present proposal deal with preparation using Reimer-Tiemann reaction which involve milder conditions and p-cyclodextrin and its derivative which lead to greater regioselectivity. The main drawback with Reimer-Tiemann reaction is that yields of aldehyde are usually low. Further drawback of the Reimer-Tiemann reaction is the formation of large quantities of side products like polymeric resinous materials from phenols and guaiacol employed. The main objective of the present invention is to provide an improved process for the production.of 2-hydroxy-4-methoxybenzaldehyde. Accordingly, the present invention provides an improved process for the preparation of 2-hydroxy-4-methoxybenzaldehyde which comprises reacting a phenolic compound , as herein defined ,with alkali hydroxide such as KOH or NaOH , in presence of cyclodextrin or its derivative such as herein defined , at a temperature in the range of 50-70°C, adding CHC13 to the above said reaction mixture over a period in the range of 5 to 1O hrs and further holding the reaction mixture at the same temperature for a period in the range of 4-8hrs, adding methylating agent, such as described herein , in situ and stirring the reaction mixture at a temperature in the range of 30 to 80°C for a period in the range of 1 to 5 hrs and recovering 2-hydroxy-4-methoxybenzaldehyde from resultant by conventional methods as described herein or recovering the phenolic aldehyde by method as described herein and converting 2, 4-dihydroxybenzaldehyde into monomethyl ether by reacting it with methylating agent in the presence of cyclodextrin or its derivative to give 2-hydroxy-4-methoxybenzaldehyde. In an embodiment of the present invention, the phenol used may be such as resorcinol, 2,4-dihydroxybenzaldehyde and resorcinol monomethyl ether. In another embodiment of the invention the alkali used may be such as KOH and NaOH. In yet another embodiment of the invention the cyclodextrin or its derivative additives employed may be such as β-cyclodextrin, heptakis-2,6-di-O-methyl-β-cyclodextrin (DMpCD), β-cyclodextrin polymer and hydroxypropyl-β-cyclodextrin. In still another embodiment the reagent employed for methylation may be such as dimethyl sulfate and methyl iodide. In a further embodiment of this invention the reagent employed for formylation may be such as CHCl3. 2-hydroxy-4-methoxybenzaldehyde may be prepared by the following steps : a. Production of 2-hydroxy-4-methoxybenzaldehyde through one pot synthesis involving Reimer-Tiemann reaction of resorcinol and methylation of the mixture, the reactions carried out in the presence of βCD, pCD-polymer, HPpCD and DMpCD b. Methylation of resorcinol and Reimer-Tiemann reaction of the methylated product. Both the reactions carried out in the presence of pCD, βCD- polymer, HPβCD and DMβCD. c. Methylation of 2,4-dihydroxybenzaldehyde in the presence of β3CD, βCD-polymer, HPβCD and DMβCD. Salient features of this reaction are: i) β-Cyclodextrin can be recovered and reused. ii) Milder reaction conditions. iii) Reimer-Tiemann reaction of resorcinol gave a maximum yield of 70.02 % of 2,4-dihydroxybenzaldehyde when the reaction was carried out in the presence of 1 equivalent of βCD iv) One pot synthesis involving Reimer-Tiemann reaction and methylation gave 48.2 % of 2-hydroxy-4-methoxybenzaldehyde when carried out in the presence of 0.2 equivalent of HPpCD. v) Reimer-Tiemann reaction of methoxyresorcinol ' (resorcinol monomethyl ether) resulted in 43.9 % of 2-hydroxy-4-methoxybenzaldehyde when carried out in the presence of 0.2 equivalent of βCD. vi) Methylation of 2,4-dihydroxybenzaldehyde by methyl iodide in the presence of 0.2 equivalents (to 2,4-dihydroxybenzaldehyde) of DMpCD gave 80.9 % of 2-hydroxy-4-methoxybenzaldehyde and 90.3% of 2-hydroxy-4-methoxybenzaldehyde with 0.5 equivalents of the βCD-polymer. vii) The procedure employed are relatively pollution free and the work up procedures are easy. The present invention provides process for the preparation of 2-hydroxy-4-methoxybenzaldehyde: a) A typical procedure employed for the Reimer-Tiemann reaction of resorcinol/resorcinol monomethyl ether comprises stirring of βCD/DMβCD/HPβCD/βCD-polymer (0.1 - 2.2 mmoles) with resorcinol/ resorcinol monomethyl ether (0.5-2.2 mmoles) at 50-70°C and 2-3 g of alkali hydroxide. Chloroform was added (6mmole - 12 mmoles) for over a period of 5-10 hrs. The reaction was further held at 50-70°C for another 4-8hrs. The work up procedure consisted of acidification and extraction with methyl ethyl ketone or butanol. The reaction product was steam distilled in some cases to obtain 2,4-dihydroxybenzaldehyde which was steam volatile. The reaction was monitored by 1H NMR spectrum by dissolving the reaction mixture in CDCl3/DMSO-d6(Table 1). Table 1. 1H NMR data of products of methylation of 2,4-dihydroxybenzaldehyde (Table Removed) b) A typical procedure employed for the methylation of 2,4-dihydroxybenzaldehyde comprises refluxing 2,4-dihydroxybenzaldehyde (1-10 mmoles), potassium carbonate (1-10 mmoles) and βCD and its derivatives (0.1 - 10 mmoles) in acetone (15 - 30 ml) during which methyl iodide (5 - 20 mmoles) was added in small portions for over a period of 1-5 hrs. The reaction mixture was then acidified and filtered. The residue of the insoluble (3CD and its derivatives were washed repeatedly with acetone and the combined washings (containing water present due to acidification) were extracted in ether or chloroform, dried and evaporated to get the compound. Here also products were analysed by 1H NMR (Table 1). In the continuous one pot synthesis where the methylation was effected immediately after the Reimer-Tiemann reaction of resorcinol, dimethyl sulphate was used as the methylating agent instead of methyl iodide and the solvent used was water and alkali-KOH instead of acetone and potassium carbonate. The proportions of the material used were as given above. In some cases methylated products were subjeeted to steam distillation to obtain 2-hydroxy-4-methoxybenzaldehyde. Commercial samples of 2,4-dihydroxybenzaldehyde, resorcinol, (3CD, potassium carbonate, potassium hydroxide, acetone, butanol, dimethyl sulfate, methyl iodide were used as such or used after purification by either distillation or recrystallization wherever applicable. βCD-polymer and DM-βCD were prepared according to the procedures of Shaw et.al.(P.E.Shaw, and B.S.Buslig, J.Agric. Food Chem., 1986, 34, 834) and Szejtli et.al (J.Szejtli, A.Liptak, I.Jodal, P.Gugedi, P.Nanasi and A.Neszmelyi, Starch/Starke, 1980, 32, 165)., respectively. HPBCD was prepared according to the procedure of J. Pitha, J. Milecki, W. Fales, L. Pannell and K. Uekama, Int. J. Phann., 1981, 29, 73) The process of the invention is described in detail in the examples given below which are illustrative only and should not be construed to limit the scope of the invention. 2,4-Dihydroxybenzaldehyde from resorcinol: Example 1 βCD (0.2202 mmoles) was stirred along with resorcinol(2.27 mmoles) at 60°C with 2.5 gof KOHin 10ml water. CHCl3(8.77 mmoles) was added over a period of 7 hrs at 0.1 ml/hr. The reaction was held at 60°C for further 4hr. The work up procedure consisted of acidification with the dilute H2SO4 and extraction with butanol, drying and evaporation of which yielded a mixture of mono and dialdehydes (2,4-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde and 2,6-dihydroxy,l,4-benzene dialdehyde along with unreacted resorcinol) which were then analysed by 1H. NMR. Example 2 PCD (0.4405 mmole) was stirred along with resorcinol (2.27 mmoles) at 60°C with 2.5 g of KOH in 10 ml water. CHCl3 (8.77 mmoles) was added over a period of 7 hrs at 0.1 ml/hr. The reaction was held at 60°C for further 4 hr. The work up procedure consisted of acidification with dilute H2SO4 and extraction with butanol, drying and evaporation of which yielded a mixture of mono and dialdehydes (2,4-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde and 2,6-dihydroxy,l,4-benzene dialdehyde along with unreacted resorcinol) which were then analysed by *H NMK. Example 3 βCD (2.203 mmoles) was stirred along with resorcinol (2.27 mmoles) at 60°C with 2.5 g of KOH in 10 ml water. CHCl3 (8.77 mmoles) was added over a period of 7 hrs at 0.1 ml/hr. The reaction was held at 60°C for further 4 hr. The work up procedure consisted of acidification with dilute H2SO4 and extraction with butanol, drying and evaporation of which yielded a mixture of mono and dialdehydes (2,4-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde and 2,6-dihydroxy,l,4-benzene dialdehyde along with unreacted resorcinol) which were then analysed by 1H NMR. Reimer-Tiemann reaction of resorcinol gave very little yield of aldehydes as the proportion of side products formed was found to be high. Measurment of area of aldehyde peaks around 9.5 ppm enabled determination of proportion of aldehydic compounds formed. The control showed a proportion of 40.4% aldehydes and 59.7% (Table 2) unreacted phenol based upon the area of aromatic protons other than those of aldehydes. The area of aldehydes and aromatic protons were measured by tracing them on a uniform tracing paper and weighing them after careful cutting. Similarly, increase in concentration of P-cyclodextrin resulted in increase in proportion of 2,4-dihydroxybenzaldehyde. Also the conversion percentage i,e the proportion of the total aldehydes formed were also found to increase accordingly. Use of one equivalent of P-cyclodextrin resulted in formation of 70.02% of 2,4-dihydroxybenzaldehyde. The proportion of total aldehydes were found to be > 61.0% for one equivalent of PCD (2.203 mmoles). For 0.8 equivalents of pCD (1.762 mmoles) where the total aldheydes formed corresponded to 61.3% of which 2,4-dihydroxybenzaldehyde was found to be 43.6%. Table 2. Products from Reimer-Tiemann reaction of Resorcinol (Table Removed) Continuous Reimer-Tiemann reaction and Methylation (one pot synthesis): Example 4 A solution of resorcinol (2.27 mmoles) in 10 ml water containing KOH (44.64 mmoles) was heated at 60°C. CHCl3 (8.77 mmoles)was added over a period of 7 hrs at 0.lml/hr. The reaction was held at 60°C for further 4 hrs. Then methylation was carried out in the same reaction mixture by adding 1.921 mmoles) for a period of 2 hrs by maintaining the temperature at 80°C . The reaction mixture was further stirred for 10 hrs. After acidification of reaction mixture with dilute H2SO4 the compounds were extracted in butanol, dried and evaporated to get the mixture of mono and dialdehydes (2,4-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde and 2,6-dihydroxy,l,4-benzene dialdehyde along with unreacted resorcinol). (CH3)SO4 was first washed with water then shaken with saturated Na2HCO3 and dried and used for methylation. Example 5 A solution of resorcinol (2.27 mmoles) in 10 ml water containing PCD(0.2202 mmole) and KOH ( 44.64 mmoles) was heated at 60°C. CHC13 (8.77 mmoles)was added over a period of 7 hrs at O.lml/hr. The reaction was held at 60°C for further 4 hrs Then methylation was carried out in the same reaction mixture by adding (CH3)SO4 ( 1.921 mingles) for a period of 2 hrs by maintaining the temperature at 80°C . The reaction mixture was further stirred for 10 hrs. After acidification of reaction mixture with dilute EbSCU the compounds were extracted in butanol, dried and evaporated to get the mixture of mono and dialdehydes (2,4-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde and 2,6-dihydroxy,l,4-benzene dialdehyde along with unreacted resorcinol). Example 6 A solution of resorcinol (2.27 mmoles) in 10 ml water containing HβCD(0.454 mmole) and KOH ( 44.64 mmoles) was heated at 60°C. CHC13 (8.77 mmoles)was added over a period of 7hrs at O.lml/hr. The reaction was held at 60°C for further 4hrs. Then methylation was carried out in the same reaction mixture by adding (CH3)2SO4 ( 1.921 mmoles) for a period of 2hrs by maintaining the temperature at 80°C . The reaction mixture was further stirred for lOhrs. After acidification of the reaction mixture with dilute H2SO4 the compounds were extracted in butanol, dried and evaporated to get the mixture of mono and dialdehydes (2,4-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde and 2,6-dihydroxy,l,4-benzene dialdehyde along with unreacted resorcinol). The yield of 2-hydroxy-4-methoxybenzaldehyde was found to be uniformly less by this procedure. The control gave only 12.5 % (Table 3) of 2-hydroxy-4-methoxybenzaldehyde. However, in all the reactions, predominantly, 2-hydroxy-4-methoxybenzaldehyde was found to be formed. An yield of 16.8 % of 2-hydroxy-4-methoxybenzaldehyde was found to be formed with 0.2 equivalent of PCD. An yield of 48.2 % of 2-hydroxy-4-methoxybenzaldehyde was formed with 0.2 equivalent of HPβCD. The reaction also gave several products which include 6-hydroxy-2-methoxybenzaldehyde, 6-hyroxy-2-methoxybenzene-l,4-dialdehydes. Table 3. Products from Reimer-Tiemann reaction of Resorcinol followed by methylation (Table Removed) Reimer-Tiemann reaction of resorcinol monomethyl ether: Example 7 To a solution of resorcinol monomethyl ether (2.22 mmoles) in 10ml water was added KOH(44.64 mmoles). To the stirred solution at 60°C was added CHC13(8.77 mmoles) for a period of 7 hrs at 0.lml/Hr. The reaction was held at 60°C for further 4hrs. The work up procedure consists of acidification with dilute and extraction by butanol , drying and evaporation of which yielded a mixture of mono and dialdehydic methoxy resorcinols which were then analysed by XH NMR. Example 8 To a solution of resorcinol mono methyl ether (2.2 mmoles) in 10 ml water was added KOH(44.64 mmoles) and 0.2 equivalent of βCD (0.44 mmole). To the stirred solution at 60°C was added CHCls(8.77 mmoles) for a period of 7 hrs at0.lml/hr. The reaction was held at 60°C for further 4 hrs The work up procedure consists of acidification with dilute H2SO4 and extraction by butanol, drying and evaporation of which yielded a mixtures of mono and dialdehydic methoxy resorcinols which were then analysed by 1H NMR. Example 9 To a solution of resorcinol mono methyl ether (2.22 mmoles) in 10 ml water was added KOH(44.64 mmoles) and 0.4 equivalent of β CD (0.88 mmoles). To the stirred solution at 60°C was added CHCl3(8.77 mmoles) for a period of 7 hrs at O.lml/hr. The reaction was held at 60°C for further 4 hrs The work up procedure consists of acidification with dilute H2SO4 and extraction by butanol, drying and evaporation of which yielded a mixture of mono and dialdehydic methoxy resorcinols which were then analysed by 1H NMR. The results have been shown in Table 5. Here also exclusive formation of 2-hydroxy-4-metb.oxybenzaldehyde was observed. However the yield of 2-hydroxy-4-methoxybenzaldehyde formed was not found to be very much different than that of the control(35.2%) when the reaction was carried out with βCD and its derivatives. There was slight increase in formation of 2-hydroxy-4-methoxybenzaldehyde with increase in βCD concentration. With 0.2 equivalent of βCD 43.94 % of 2-hydroxy-4methoxybenzaldehyde was formed. With 0.5 equivalent of βCD polymer 30.21 % of 2-hydroxy-4-methoxybenzaldehyde was formed. Table 4. Product distribution in methylation of 2,4-dihydroxybenzaldehyde as determined by 1HR NMR Conditions Equivalents (Table Removed) Methylation of 2,4-dihydroxybenzaldehyde: Example 10 2,4-DihydroxybenzaIdehyde (7 mmoles) was refluxed with potassium carbonate (7 mmoles) in acetone (20 ml). Methyl iodide (15.6 mmoles) was added in small portions for over 2-3 hours after which period the reaction mixture was acidified with dil.H2SO4 and filtered. Insoluble βCD was washed repeatedly with acetone and the combined washings were dried and evaporated. The proportions of 2-hydroxy-4-methoxybenzaldehyde and 2,4-dimethoxybenzldehyde were determined by 1H NMR spectroscopy. The results of methylation with methyl iodide are presented in Table 4 . Under the reaction conditions employed, 2,4-dihydroxybenzaldehyde (1) gave 2-hydroxy-4-methoxybenzaldehyde (2)- 77.6% and unreacted 1 - 22.4%. On steam distillation of the crude reaction mixture about 47.9% of 2-hydroxy-4-methoxybenzaldehyde (99.0% purity) was obtained. Table 5. Products from Reimer-Tiemann reaction of resorcinol monomethyl ether (Table Removed) Example 11 2,4-Dihydroxybenzaldehyde (7 mmoles) was refluxed with potassium carbonate (7 mmoles) and PCD (7 mmoles)in acetone (20 ml). Methyl iodide (15.6 mmoles) was added in small portions for over 2-3 hours after which period the reaction mixture was acidified with dil.H2SO4 and filtered. Insoluble pCD was washed repeatedly with acetone and the combined washings were dried and evaporated. The proportions of 2-hydroxy-4-methoxy benzaldehyde and 2,4-dimethoxybenzaldehyde were determined by 1H NMR spectroscopy. The reaction in which about 0.39 equivalent of PCD was present, yielded 63.6% compound of 2 and 36.4 % of compound 3(2,4-dimethoxybenzaldehyde), but no compound 1 and 4 (4-hydroxy-2-methoxybenzaldehyde) was obtained. However, the presence of higher equivalents of pCD not only reduced the proportions of compound 3 and 1 (9.2% and 20.4% with 0.76 equivalent pCD and 10.8% and 11.8% with one equivalent of BCD respectively) but also increased the proportions of compound 2 (70.4% and 77.4% for 0.39 and 1.0 equivalent respectively). However, the proportion of compound 2 formed with one equivalent of βCD was found to be comparable to that obtained with control. Example 12 2,4-Dihydroxybenzaldehyde (7 mmoles) was refluxed with potassium carbonate (7 mmoles) BCD-polymer (3.5 mmoles) in acetone (20 ml). Methyl iodide (15.6 mmoles) was added in small portions for over 2-3 hours after which period the reaction mixture was acidified with dil H2SO4and filtered. Insoluble BCD was washed repeatedly with acetone and the combined washings were dried and evaporated. The proportions of 2-hydroxy-4-methoxybenzaldehyde and 2,4-dimethoxybezaldehyde were determined by 1H. NMR spectroscopy. The presence of 0.49 equivlents of βCD-polymer gave 90.3 %, 4.6% and 5.1 % of 2,3 and 1 respectively. Similarly, the presence of only 0.21 equivalent of DMBCD gave about 80.9 % compound 2(2-hydroxy-4-methoxybenzaldehyde), 6.4% of compound 3 (2,4-dimethoxybenzaldehyde) and 12.7% of compound 1 (2,4-dihydroxybenzaldehyde). Although the control exhibited 100% selectivity with respect to 2, the proportions of 2 formed especially with DMBCD and BCD-polymer were definitely higher. It is of interest to note that both compounds 2 and 3 possess flavour value. The main advantages of the invention achieved are: Use of β-cyclodextrin and its derivatives resulted in greater selectivity in the production of 2-hydroxy-4-methoxybenzaldehyde from i) Reimer-Tiemann reaction of resorcinol resulted in the formation of 70.02 % of 2,4-dihydroxybenzaldehyde inthe presence of 1 equivalent of BCD. ii) Continuous Reimer-Tiemann reaction and melthylation reaction resulted in the formation of 48.2% 2-hydroxy-4-methoxybanzaldehyde in the presence of 0.2 equivalent of HPβCD. iii) Reimer-Tiemann reaction of the resorcinol monomethyl ether reaction mixture resulted in 43.9% of 2-hydroxy-4-methoxybenzaldehyde in the presence of 0.2 equivalent of βCD. iv) Methylation of 2,4-dihydroxybenzaldehyde by methyl iodide led to the formation of 90.3% of 2-hydroxy-4-methoxybenzaldehyde along with minor proportions of unreacted 2,4-dihydroxybenzaldehyde (5.1%) and 2,4- dimethoxybenzaldehyde in the presence of 0.5 equivalents of βCD-polymer. We claim: 1 An improved process for the preparation of 2-hydroxy-4-methoxybenzaldehyde which comprises reacting a phenolic compound , as herein defined ,with alkali hydroxide such as KOH or NaOH , in presence of cyclodextrin or its derivative such as herein defined , at a temperature in the range of 50-70°C, adding CHC13 to the above said reaction mixture over a period in the range of 5 to 1O hrs and further holding the reaction mixture at the same temperature for a period in the range of 4-8hrs, adding methylating agent, such as described herein , in situ and stirring the reaction mixture at a temperature in the range of 30 to 80°C for a period in the range of 1 to 5 hrs and recovering 2-hydroxy-4-methoxybenzaldehyde from resultant by conventional methods as described herein or recovering the phenolic aldehyde by method as described herein and converting 2, 4-dihydroxybenzaldehyde into monomethyl ether by reacting it with methylating agent in the presence of cyclodextrin or its derivative to give 2-hydroxy-4-methoxybenzaldehyde. 2. An improved process as claimed in claim 1 the phenolic compound used is selected from resorcinol, 2,4-dihydroxybenzaldehyde and resorcinol monomethyl ether. 3. An improved process as claimed in claims 1 to 2 the cyclodextrin or its derivative additives employed is selected from (3-cyclodextrin, heptakis-2,6-di-O-methyl-p- cyclodextrin (DMPCD), p-cyclodextrin polymer and hydroxypropyl-(3-cyclodextrin. 4. An improved process as claimed in claims 1 to 3 the methylating agent used is selected from dimethyl sulfate and methyl iodide. 5. An improved process for the preparation of 2-hydroxy-4-methoxy benzaldehyde substantially as herein described with reference to examples.

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