A General Strategy for the Synthesis of Truxinate Natural Products Enabled by Enantioselective [2+2] Photocycloadditions.

Pseudodimeric cyclobutanes constitute a large class of natural products that could, in principle, be efficiently synthesized via [2+2] photocycloadditions. However, the difficulty in developing chemo-, regio-, diastereo-, and enantioselective cycloadditions has limited their use in asymmetric syntheses. Herein, we show that chiral acid catalysts promote highly selective visible-light photocycloadditions, the products of which can be quickly transformed into truxinate natural products. This general approach has enabled the synthesis of both dimeric and pseudodimeric cyclobutane natural products with excellent enantioselectivity.

Au(I)-Catalyzed Synthesis of Trisubstituted Indolizines from 2-Propargyloxypyridines and Methyl Ketones.

A new Au(I)-catalyzed method for the preparation of trisubstituted indolizines from easily accessible 2-propargyloxy-pyridines is reported. The reaction tolerates a wide range of functionality, allowing for diversity to be introduced in four distinct regions of the product (R, R1, R2, and Ar). The proposed mechanism proceeds via enol addition to an allenamide intermediate and explains the observed increase in yields when electron poor methyl ketones are utilized.