Elektronenstossinduzierte fragmentierung von acetylenverbindungen—XII
作者:H. Schwarz、C. Köppel、F. Bohlmann
DOI:10.1016/s0040-4020(01)97065-6
日期:1974.1
In contradiction to previous concepts, electronimpactinducedmigrations of TMS-functions are possible in configuratively fixed systems, if electronimpact results in a change of the molecular geometry which causes an interaction of non-bonded centers. The bis-TMS-derivatives of 1,2-, 1,3-and 1,4-phenols can be distinguished clearly whereas for the phenols this is possible only with limitations.
demonstrated for the first time that conjugated enynes can be employed as a facile substrate in olefin metathesis with the use of a bispyridine-substituted ruthenium benzylidene catalyst. Cross-metathesis of the enynes with alkenes turns out to proceed with preferential formation of (Z)-isomers over (E)-isomers up to >25:1 in moderate to good yields. The intramolecular version of conjugated enynes affords
Bismuth bromide-catalyzed reductive coupling of carbonyl compounds and its application to the synthesis of novel crownophanes
作者:Naoki Komatsu、Jun-ya Ishida、Hitomi Suzuki
DOI:10.1016/s0040-4039(97)01720-6
日期:1997.10
The reductive homocoupling of carbonylcompounds and heterocoupling of a carbonylcompound with an alkoxysilane were both effected smoothly with triethylsilane in the presence of a catalytic amount of bismuth bromide (1–3 mol%) under mild conditions. This ether-forming reaction was successfully applied to the single-step preparation of novel crownophanes with olefinic or acetylenic linkages.
convert alkenes, unsaturated aliphatic alcohols, and aryl boronic acids into secondary benzylic alcohols with high stereoselectivities (typically >95:5 er) under sequential catalysis that integrates alkene cross-metathesis, isomerization, and nucleophilic addition. Prochiral allylic alcohols can be converted to any stereoisomer of the product with high stereoselectivity (>98:2 er, >20:1 dr).
Cross-Metathesis of the Vinyl Group on Tetrapyrrolic Macrocycles: Reactivity, Selectivity, and Mechanism
作者:Xin Liu、Ethan Sternberg、David Dolphin
DOI:10.1021/jo8007989
日期:2008.9.1
To find a general strategy for modifying the peripheral structure of vinylchlorin and porphyrin substrates, cross-metathesis on the vinylgroup of these tetrapyrrolic macrocycles was investigated. The N-heterocyclic carbene-containing ruthenium complex 3 efficiently catalyzed the cross-metathesis (CM) of vinylchlorins and vinylporphyrins with a variety of olefins in high E-stereoselectivity. Different