Lewis acid-catalyzed asymmetric hetero Diels-Alder cycloaddition of a 1-Thiabuta-1,3-diene with Chiral N-Acryloyl- and N-Crotonoyl-oxazolidinone dienophiles
Me2AlCl- and TiCl4-catalyzed asymmetric hetero Diels-Alder cycloaddition reactions of 2,4-diphenyl-1-thiabuta-1,3-diene with (S)-N-acryloyl- and (S)-N-crotonoyl-4-benzyl-1,3-oxazolidin-2-one dienophiles are described in which not only the sense of the π-facial selectivity but also the degree dramatically varied as a function of stoichiometry of the added Lewis acids.
Me 2 AlCl-和TiCl 4催化的2,4-二苯基-1-硫代丁1,3-二烯与(S)-N-丙烯酰基-和(S)-N-巴豆酰基-的不对称杂Diels-Alder环加成反应描述了4-苄基-1,3-恶唑烷基-2-酮二烯亲和物,其中不仅π-面选择性的意义而且其程度根据所添加的路易斯酸的化学计量而显着变化。
Ytterbium triflate-catalyzed asymmetric hetero Diels-Alder cycloaddition of a 1-thiabuta-1,3-diene with a chiral N-acryloyloxazolidinone dienophile. Diastereoface control by solvents or achiral additives
作者:Takao Saito、Mikako Kawamura、Jun-ichi Nishimura
DOI:10.1016/s0040-4039(97)00520-0
日期:1997.5
Ytterbium triflate [Yb(OTf)3]-catalyzed asymmetric hetero Diels-Alder cycloaddition reaction of 2,4-diphenyl-1-thiabuta-1,3-diene with (S)-N-acryloyl-4-benzyl-1,3-oxazolidin-2-one is described in which the sense of the π-facial selectivity can be controlled by solvents or additives employed without altering the auxiliarychirality for the asymmetric induction.
The catalytic, highly enantioselective hetero-DielsâAlder reactions of thiabutadienes using homochiral copper and nickel triflate and perchlorate bis(oxazoline) and bis(imine) complex catalysts to afford optically active dihydrothiopyrans are described for the first time.
Uncatalysed (thermal) and Lewis acid-promoted asymmetric hetero-Diels–Alder reaction of 1-thiabuta-1,3-dienes (thiochalcones) with di-(–)-menthyl fumarate. Configuration determination by X-ray crystallographic analysis of (2S,3R,4R)-(+)-2,3-bis[(–)-menthoxycarbonyl]-4,6-diphenyl-3,4-dihydro-2H-thiopyran and conversion of cycloadducts into optically pure diols
1-Thiabuta-1,3-dienes 1 (thiochalcones) underwent asymmetric hetero-Diels–Alder reaction with di-(–)-menthyl fumarate 2 to afford a mixture of 3,4-cis-(3 and 4) and 3,4-trans-dihydrothiopyrans (5 and 6) in good-to-excellent chemical yield with fair diastereoselectivities, the stereoisomer 3 predominating. An endo(3,4-cis): exo(3,4-trans) selectivity was observed in the ratio 98–85:2–15. The uncatalysed