A Short and Efficient Synthesis of 3-Spiro-α-methylene-γ-butyrolactone Oxindolones from Isomerised Bromo Derivatives of Morita-Baylis-Hillman Adducts

A short and efficient synthesis of alpha-methylene-gamma-butyrolactone-3-spirooxindolones by the reaction of isomerised bromo derivatives of Morita-Baylis-Hillman adducts of isatin and formalehyde followed by acid-catalysed lactonisation has been achieved. The oxindolidino allyl bromide has been used for the first time for the allylation of aldehydes to afford a 2-oxindolidino homoallylic alcohol which on acid-catalysed lactonisation delivered the title compounds in excellent yield. Synthetic transformation of the spirolactone oxindole is demonstrated with the preparation of an oxirane derivative and a second Morita-Baylis-Hillman adduct.