Catalytic Enantioselective Nazarov Cyclization. Issue 40 (30th October 2017) - Jolit, Anais
Abstract : A detailed account of an asymmetric Nazarov cyclization that leads to α‐hydroxycyclopentenones bearing either vicinal, all‐carbon quaternary centers, or vicinal quaternary and tertiary centers is given. The all‐aliphatic examples represent the greatest challenge, as the dienone starting materials are not activated toward cyclization by an aryl group. The rational design and optimization of the substrates in parallel with optimization of the chiral Brønsted acid catalyst is also described, as well as a series of diastereoselective transformations of a fully substituted cyclopentenone product. Abstract : An asymmetric Nazarov cyclization catalyzed by a 1, 1′‐bi‐2‐naphthol‐derived N ‐triflylphosphoramide leads to cyclopentenones with all‐aliphatic all‐carbon vicinal stereocenters with enantiomeric ratios of up to 99:1. The cyclic products can be modified by a number of highly specific reactions to form sterically congested cyclopentenones incorporating up to three contiguous quaternary centers.