Regioselective Palladium-Catalyzed Formate Reduction of N-Heterocyclic Allylic Acetates

Link: http://pubs.acs.org/cgi-bin/abstract.cgi/joceah/asap/abs/jo0624896.html

From Prof. Duen-Ren Hou's group at National Central University, Taiwan

A recent article appeared in JOC Note ASAP detailing a method for reductive deacetylation of allylic acetate using Pd catalyst and formate as a source for hydride.

The method was aimed to be applied to N-heterocycles obtained as a product from Grubbs' RCM reaction to selectively afford an exo-methylene heterocycle as the end product. The reaction was shown to work well with various ring sizes. The following tables and scheme (taken directly from their paper) show the details of their findings.

The construction of substrates by simple alkylation with allyl bromide derivatives followed by Gubbs' RCM.

Their massive experiments with the 5-membered 1a. Note: (a) Ratios were determined by 500 MHz 1H NMR of crude reaction mixtures. (b) Not detected. (c) Isolated yield, 68%.

Experiments with 6-membered 1bExperiments with 7-membered 1c

With 8-membered 1d

6-membered product 5b was further oxidized with RuCl3 to give ketone 7.