Regioselective reaction of dihydromyrcene: rapid syntheses of cyclic esters and their open-chain analogs with excellent olfactory value

In the present study the condensation of dihydro-myrcene (DHM) with carboxylic acids in the presence of BF₃OEt₂ yields the condensation ester products (60%-90%). At low temperature, stirring for 90 min at 0-30 °C mainly open-chain condensation products, involving the condensation of only one (2-3) double bond, are formed. However, on heating the reaction mixture to 40-60 °C for 90 min., the cyclized products is increased up to 90%. In previous study, the molar ratio of the dihydromyrcene (DHM) to acetic acid to sulphuric acid with 1:3:0.2, at 60 °C and the reaction time of 6.5 h yielded 1-(3,3-dimethylcyclohexyl)ethyl acetate (45.3%). The nucleophilic substitution of chloro- ester with second acid yields di-esters. The products are characterised by IR, ¹H,¹³C NMR, GC, GC/HRMS analyses. All products showed ester band in FTIR in the range of 1730-1760 cm^-1. The product display excellent odour value.