Cesium fluoride-mediated claisen rearrangement of aryl propargyl ether and its application to the synthesis of chelerythrine.

Abstract

In the presence of cesium fluoride, the Claisen rearrangement of aryl propargyl ethers selectively provided 2-methylbenzofurans, which was successively treated with osmium tetroxide, periodic acid and 5% sodium hydroxide to give salicylaldehydes in good yields. The method was used to synthesize chelerythrine (2) via the common intermediate (8) prepared by the two routes as shown in Chart 3.