Asymmetric Organocatalytic Synthesis of Fluorinated β‐Hydroxy Diazenes

Abstract

The nucleophilic addition of formaldehyde tert‐butyl hydrazone to fluoromethyl ketones provides a valuable tool for the synthesis of highly functionalized β‐hydroxy β‐tri‐ and difluoromethyl diazenes. Excellent reactivities and moderate to good enantioselectivities (up to 90 % ee) were achieved by H‐bonding activation exerted by tert‐Leucine derived H‐bonding (squaramide or thiourea) organocatalysts. Subsequent derivatizations in one‐pot fashion provide synthetically useful intermediates for target‐oriented synthesis: tri‐ and di‐fluoromethylated azoxy compounds, β‐amino alcohols, α‐hydroxy aldoximes and derivatives thereof.