Preparation of Heliotropyl Chloride

Heliotropin (also known as piperonal, or 3,4-methylenedioxy-benzaldehyde and having the structural formula is an important aroma and flavour chemical and is also an intermediate in syntheses of other aroma chemicals and some pharmaceutical chemicals. 

In general heliotropin is manufactured from safrole, which is a component of many 

It has also been suggested to manufacture heliotropin starting from catechol (J. Gen. Chem., USSR, 1938, 8, 1975). This method involves a 3-step process which comprises 1) the preparation of methylenedioxybenzene from catechol, 2) the conversion of methylenedioxybenzene with paraformaldehyde and hydrogen chloride to heliotropyl chloride and 3) the reaction of the latter with hexamethylenetetramine in ethanol to obtain heliotropin with an overall yield of 11—28 % based on catechol. An improvement in the yield of step 1), and thus overall yield, can be obtained by employing a process for preparation of methylenedioxybenzene from catechol as described in U.K. patent specification 1,097,270 which involves the reaction of catechol with a methylene dihalide under alkaline conditions in the presences of a highly polar, aprotic solvent. 

---