Highly stereoselective syntheses of conjugated , - and , -dienes, -enynes and -1,2,3-butatriened via alkenylborane derivatives
摘要:
A highly selective and potentially general methodology for the synthesis of conjugated E,E- and E,Z-dienes, E-enynes, and E-1,2,3-butatrienes via hydroboration of alkynes is reported. The observed stereoselectivity was > 98-99%.
Stereoselective Ring Expansion of Vinyl Oxiranes: Mechanistic Insights and Natural Product Total Synthesis
作者:Matthew Brichacek、Lindsay A. Batory、Jon T. Njardarson
DOI:10.1002/anie.200906830
日期:2010.2.22
applicable, catalytic, and stereoselective vinyl oxirane ringexpansion is described (see scheme; hfacac=hexafluoroacetylacetonate). The stereoselectivity was influenced by several reaction parameters, and kinetic studies support a mechanistic proposal involving the in situ formation of a more reactive catalytic species. This ring‐expansion reaction has been employed in the asymmetric total synthesis
and have been shown to be capable of heterolysis of molecular hydrogen, a property that has led to their use in hydrogenation reactions of polarized multiple bonds. Here, we describe a general approach to the hydrogenation of alkynes to cis-alkenes under mild conditions using the unique ansa-aminohydroborane as a catalyst. Our approach combines several reactions as the elementary steps of the catalytic
Ni-Catalyzed Si−B Addition to 1,3-Dienes: Disproportionation in Lieu of Silaboration
作者:Martin Gerdin、Christina Moberg
DOI:10.1021/ol060765x
日期:2006.7.1
[reaction: see text] Upon attempted silaboration of acyclic 1- and 1,4-substituted 1,3-dienes, a new disproportionationreaction was discovered, yielding 1:1 mixtures of allylsilanes and dienylboranes. It was demonstrated that, as a key step in this new catalytic process, hydrogen is being transferred from one diene moiety to another.
Stereoselective method for synthesizing (E)-, (E,Z)- and (E,E)-conjugated dienes via alkylation of 3-sulfolenes as key step is developed. Sex pheromones with (E)- and (E,E)-conjugated diene structures are synthesized with exclusively high stereoselectivity by applying the method.
Synthesis of 1,4-disubstituted (E,Z)-1,3-dienes from lithium dicyclohexyl(trans-1-alkenyl)(1-alkynyl)borates
作者:George Zweifel、Stephen J. Backlund
DOI:10.1016/s0022-328x(00)84873-1
日期:1978.8
Treatment of lithium dicyclohexyl(trans-1-alkenyl)(1-alkynyl)borates with either boron trifluoride etherate or tri-n-butyltin chloride results in the preferential migration of the alkenyl group from boron to the adjacent alkynyl carbon atom. Protonolysis of the resultant organoboron intermediates with acetic acid affords the corresponding 1,4-disubstituted (E,Z)-1,3-dienes in good yields, provided