Regio- and stereoselective cyclopropanation of functionalised dienes. Novel methodology for the synthesis of vinyl- and divinyl-cyclopropanes
摘要:
Dienes, bearing an electron-withdrawing substituent at C-1, are cyclopropanated regio- and stereo selectively at the C-C double bond proximal to this electron-withdrawing group. The highest selectivity is observed in the case of dienylboronates. The cyclopropanation of these substrates affords almost exclusively the synthetically useful 1-boronato-2-vinyl-cyclopropanes. (C) 2002 Elsevier Science Ltd. All rights reserved.
Practical Synthesis of (E)-α,β-Unsaturated Carboxylic Acids Using a One-Pot Hydroformylation/Decarboxylative Knoevenagel Reaction Sequence
作者:Susanne T. Kemme、Tomáš Šmejkal、Bernhard Breit
DOI:10.1002/adsc.200700595
日期:2008.5.5
AbstractCombining the regioselective room temperature/ambient pressure hydroformylation and a modification of the Doebner–Knoevenagel reaction allowed for the development of an efficient, one‐pot procedure for the synthesis of (E)‐α,β‐unsaturated carboxylic acids. The reaction proceeds under mild conditions, tolerates a variety of functional groups and gives (E)‐α,β‐unsaturated carboxylic acids in good yields and with excellent regio‐ and stereocontrol. The practicability of this process has been demonstrated by a short protecting group‐free synthesis of the queen honeybee pheromones 9‐ODA [(E)‐9‐oxodec‐2‐enoic acid] and 9‐HDA [(E)‐9‐hydroxydec‐2‐enoic acid].