Samarium(II)-mediated 4-exo trig ketyl-olefin cyclisation of unsaturated aldehydes. A general, stereoselective synthesis of functionalised cyclobutanols
作者:Derek Johnston、Catherine M. McCusker、David J. Procter
DOI:10.1016/s0040-4039(99)00910-7
日期:1999.6
gamma,delta-Unsaturated aldehydes having a quaternary centre in either the a or beta-position, have been prepared from substituted gamma-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. (C) 1999 Elsevier Science Ltd. All rights reserved.
Samarium(II)-mediated 4-exo-trig cyclisations of unsaturated aldehydes. A stereoselective approach to functionalised cyclobutanols
作者:Derek Johnston、Catherine F. McCusker、Kenneth Muir、David J. Procter
DOI:10.1039/a909549g
日期:——
γ,δ-Unsaturated aldehydes having a fully substituted centre in either the α- or β-positions, have been prepared from substituted γ-butyrolactones and undergo efficient 4-exo-trig cyclisation on treatment with samarium(II) iodide to give functionalised cyclobutanols. In all cases cyclisation occurs with complete diastereocontrol to give anti-cyclobutanol products. The stereochemistry of the products has been confirmed by NOE and X-ray crystallographic studies. In the cyclisation of substrates having a third substituent on the double bond, α- to the ester, significant control is achieved at the third newly formed stereocentre lying outside the ring. The origin of the stereoselectivity at this third centre and its marked dependence on cosolvent are discussed.