Chap. 29 Reactions of Interest in Medicinal Chemistry

Abstract

This chapter focuses on some new and/or novel reactions that are of interest in medicinal chemistry. The reactions described in the chapter are grouped in a classical manner as far as possible. Various researchers offer a condensed and critical evaluation of modern basic synthetic methods. The continuous investigation of various addition reactions gives unique synthetic methods for the preparation of new types of compounds. Methods of reduction are constantly being explored and hydrogenation with homogeneous catalysts has the advantage of being unaffected by the usual catalyst poisons. The reduction can be performed under relatively mild conditions as illustrated by the hydrogenation of methyl linoleate in the presence of iron pentacarbonyl catalyst—Fe(CO) 5 —to produce a monoene in 65.5% yield at 100 °C and 400 psi. The homogeneous catalytic hydrogenation of acetylenes gives quantitative yield of the corresponding alkanes. Hydrogenation occurred at less than 1 atm. at 20 °C using 0.005 mole (Ph 3 P) 3 RhCl and 2 moles of the acetylene all dissolved in a mixture of ethanol-benzene. Diimide (H 2 N 2 ) reductions have been reported many times and continuous work on their selectivity is underway. Diimide is used in the reduction of aldehydes and ketones to the corresponding alcohols. Aliphatic carbonyls are reduced slowly and the yield is low (max 14%), whereas aromatic aldehydes and ketones gives yields as high as 56%.