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.
Non-Covalent Carbonyl-Directed Heck-Matsuda Desymmetrizations: Synthesis of Cyclopentene-Fused Spirooxindoles, Spirolactones, and Spirolactams
作者:Shivashankar Kattela、Gabriel Heerdt、Carlos R. D. Correia
DOI:10.1002/adsc.201600946
日期:2017.1.19
Enantioselective carbonyl‐directable Heck reactions using aryldiazonium salts were developed with the aim to construct chiral quaternary spiro centers in an efficient manner. Five‐ and six‐membered spirooxindoles, spirolactones, and spirolactams (36 examples) were obtained in good to excellent isolated yields with diastereoselectivities ranging from 13:1 to >20:1, and enantiomeric excesses up to 99%