One‐Pot Preparation of Chiral Carbacycles from Morita–Baylis–Hillman Carbonates by an Asymmetric Allylic Alkylation/Olefin Metathesis Sequence

Abstract

An operationally simple, one‐pot synthetic protocol for the formation of all‐carbon, highly substituted five‐ and six‐membered rings is described. In this two‐step procedure, an asymmetric allylic alkylation (AAA) of Morita–Baylis–Hillman (MBH) carbonates with allylmalononitrile, catalyzed by a chiral tertiary amine, is followed by a ring‐closing alkene metathesis (RCM) reaction. Products are obtained in high yields, and an excellent level of optical purity of some of the target compounds is achieved after just a single recrystallization.

Unconventional Transformations of Morita–Baylis–Hillman Adducts

“…The same year, Veselý and co-workers disclosed a onepot multi-catalytic synthesis of five-and six-membered carbocycles 24a,b from MBH carbonates 10 and alkenylsubstituted malononitriles 22a,b by means of Lewis base and Ru catalysis (Scheme 3B). 25 After the allylic alkylation step, the Hoveyda-Grubbs catalyst 23 is added to the reaction mixture, delivering the final product 24a,b through ring-closing metathesis (RCM). High dilution (c = 0.002 M) as well as high temperature (100 °C) were crucial to avoid product dimerisation and to overcome the intrinsic low reactivity of acrylates towards RCM.…”