Preparation process of cystic fibrosis transmembrane conductance regulator modulators

摘要

A process for the preparation of a compound of Formula 8 ** (See formula) ** which comprises nitrating a compound of Formula 7 using a mixture of sulfuric acid and nitric acid in the presence of dichloromethane ** (See formula) ** in the that PG is a protective group and R2 and R4 are each tert-butyl, and in which the nitro compound of Formula 8 is purified by crystallization, in which PG is propoxyphenyl, methanesulfonyl, 4-nitro-benzoyl, ethoxyformal, butoxyformate , t-butoxyformal, i-propoxyformal or methoxyformal.