Regioselektive Reduktionen von cyclischen Thienospiroanhydriden

摘要

Regioselective reduction of unsymmetrically substituted spiroanhydrides (A1and3) with reducing agents such as sodium boranate, lithium boranate, dimethylamine borane and lithium- or potassium-tri-(sec-butyl)boranate yielded the spirocyclic lactones1and2or4and5, respectively. The influence of the temperature and the sequence of addition of reducing agents on the ratio of the spirocyclic lactones formed was studied in order to obtain a high degree of regioselectivity. Sterical and mechanistic aspects are discussed in order to explain the results.