Catalytic conversion of β-hydroxy carboxylic acids to olefins by tungsten(Vi) complexes: A new acyl group transfer catalyst

Oxotungsten tetrachloride catalyzes the conversion of β-hydroxy carboxylic acids to olefins, in the presence of base. The reaction proceeds in high yield, stereospecifically, and with high catalyst turnover. Examination of the likely stoichiometric steps for β-hydroxy carboxylic acid activation shows the formation of intermediate chelates, structures of which were studied by¹H NMR. The role of the base was probed by using both¹H and¹⁸³W NMR, and it was shown that base simply deprotonates the chelate; base does not coordinate to the W center. β-Lactones were the initial products of this sequence from which decarboxylation occurred to give the olefinic product.