Synthesis of Novel Optically Active Tin Hydrides Containing Chiral Ligands
作者:Kay Schwarzkopf、Jürgen O. Metzger、Wolfgang Saak、Siegfried Pohl
DOI:10.1002/cber.19971301030
日期:1997.10
The synthesis of the chiraltin bromides 1-4 and hydrides 5-8, containing the potentially bidentate, opticallyactive 2-[ (1 S/R)- 1 -dimethylaminoethyl]phenyl and 2 -[( 1 S) - 1 -dimethylamino-2,2-dimethylpropyl]phenyl ligands, is reported. The tinhydrides 5-8, with the tin atom as the stereogenic centre, were isolated as diastereomeric mixtures with diastereomeric ratios of dr = 50:50 up to dr =
Various fumaric acid diamides were alkylated by reaction with photogenerated radicals. The radicals were produced either by benzophenone triplet hydrogen abstraction (from 1,3-dioxolane, 2-methyl-1,3-dioxolane and adamantane) or via photoinduced electron transfer sensitised by DCN/biphenyl from stannanes (t-BuSnPh3 and Bu4Sn). When chiral substrates were employed the reaction occurred with a good degree of stereoselectivity even when acyclic alkyl radicals were involved. (C) 2000 Elsevier Science Ltd. All rights reserved.
Tandem energy transfer–electron transfer in the photosensitized alkylation of α,β-unsaturated ketones
alpha,beta-Unsaturated ketones are not conveniently alkylated by radicals generated from tetraalkylstannanes via photoinduced electron transfer (PET), either by direct irradiation or when a singlet sensitizer (an aromatic nitrile, a pyrilium salt) is used, However, the procedure is successful with tetramethyl pyromellitate (TMPM) as the sensitizer, TMPM is promoted to the triplet state by energy transfer from the unsaturated ketones and then sensitizes the cleavage of alkylstannanes by electron transfer, The alkyl radicals thus formed finally add to the unsaturated ketones, giving the beta-alkyl derivatives. (C) 1997 John Wiley & Sons, Ltd.
New chiral tin compounds containing the 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand
compounds containing the optically active 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand and tert-butyl, methyl and/or phenyl groups on the tin has been synthesized. All the novel compounds have been characterized, especially by means of the multinuclear NMR investigation, the results of which are discussed. The tin halides, as pairs of diastereoisomers in solution, crystallize in the form of one diastereoisomer