Addition of a Silyl Ketene Acetal to α,β-Unsaturated Cyclic Anhydrides

Abstract

Addition of [1-methoxy-2 methyl-1-propenyl)-oxy] trimethylsilane (MTS) to unsymmetrical α,β-unsaturated cyclic anhydrides (namely, itaconic anhydride and citraconic anhydride) as well as symmetrical anhydrides (namely, maleic anhydride and 2,3-dimethylmaleic anhydride) was investigated. Itaconic anhydride isomerizes to citraconic anhydride in the presence of MTS. In the presence of Lewis acid catalysts (Yb(OTf)₃/CH₂Cl₂), MTS adds to itaconic anhydride at room temperature in a 1,4-fashion. 1,2-Addition is the preferred pathway with both 2,3-dimethyl maleic anhydride and citraconic anhydride.

Keywords:

• 1,2-Addition
• 1,4-addition
• cyclic anhydrides
• Lewis acid
• silyl ketene acetal

ACKNOWLEDGMENT

R. G. thanks the Council for Scientific and Industrial Research, New Delhi, for a senior research fellowship.

Notes

Note. Order of addition: itaconic anhydride + Lewis acid + solvent + MTS (1.2 equivalents).

^a 2.46 mmol.

^b 1.2 equivalents.

^c The isolated product was citraconic anhydride.

^a 1.2 equivalents.

^a 2.46 mmol.

^b 1.2 equivalents.