... 0040-4039(95)00638-9 Tetrahedron Letters, Vol. 36, No. 22, pp. 3905-3908, 1995 Elsevier Science Ltd Printed in Great Britain 0040-4039/95 $9.50+0.00 ... When the Wittig reaction was carried out with hexachloroacetone (HCA) the butenoate (IV) was formed in 22% yield. ...