Reactions with α-diazo-ketones. Part II. Intramolecular cyclisation of bisdiazo-ketones

Abstract

Catalytic decomposition of 1,5-bisdiazo-3,3-bis-(2-methylprop-2-enyl)pentane-2,4-dione (1b) and its 3-(but-3-enyl)-3-(prop-2-enyl) analogue (1c) yielded the spirobi{bicyclo[3.1.0]hexane}dione (4) and its analogue (12), respectively, both formed by intramolecular double addition of the intermediate bisketocarbene systems to the olefinic bonds. As by-products, isomeric spiro-lactones (7) and (8) were obtained. Assignment of stereochemistry to the products is based on n.m.r. spectral properties and/or chemical transformations.