Tandem reaction of α-hypervalent iodo functionalized phosphonium and arsonium ylides as umpolung reagents

α-Hypervalent iodo functionalized phosphonium and arsonium ylides 2 can be used as umpolung ylides to react with nucleophiles to give α-heteroatom substituted ylides 4 in good yields. A tandem sequence of nucleophilic substitution then Wittig reaction occurs smoothly to form (Z)-α-halo-α,β-unsaturated esters 6, stereoselectively, in moderate to excellent yields.