Samarium(II)-mediated 4-exo trig ketyl-olefin cyclisation of unsaturated aldehydes. A general, stereoselective synthesis of functionalised cyclobutanols

Article abstract of DOI:10.1016/S0040-4039(99)00910-7

γ,δ-Unsaturated aldehydes having a quaternary centre in either the α or β-position, have been prepared from substituted γ-butyrolactones and undergo efficient 4-exo-trig ketyl-olefin cyclisation on treatment with samarium(II) iodide to give functionalised cyclobutanols. In all cases cyclisation occurs with complete diastereocontrol to give anti-cyclobutanol products. In the cyclisation of substrate 4ab, significant stereochemical control is achieved at three contiguous chiral centres. Both unsaturated esters and vinyl sulfones have been employed as substrates in the reaction.