Conformational analysis of benzoanellated nine-membered rings, Part 1. 1,4,5,7-tetrahydro-3H-2,6-benzodithionin derivatives
作者:Barbara Rys、Helmut Duddeck、Monika Hiegemann
DOI:10.1016/s0040-4020(01)86418-8
日期:1991.1
The NMR spectra of compounds 1–5, recorded at different temperatures, are discussed and interpreted in terms of conformational equilibrium. Ground state conformations are found to be chiral, ring inversionbarriers are surprisingly high (ca 48 kJ/mol).
The Acid-catalyzed Reaction of Isocyanide with Oxetane
作者:Takeo Saegusa、Naotake Taka-ishi、Yoshihiko Ito
DOI:10.1246/bcsj.44.2473
日期:1971.9
The reaction of isocyanide with oxetane in the presence of BF3·OEt2 was studied; in this reaction a 1:1 cyclic adduct, 2-iminotetrahydrofuran, was formed. From 2-methyloxetane, 2-imino-5-methyltetrahydrofuran was exclusively formed. These findings suggest an SN2 mechanism for the cleavage of the oxetane ring. Oxetanes with electron-withdrawing substituents gave γ-alkoxybutyronitrile as the main product
report a cobalt-catalysed enantioselective aza-Barbier reaction of ketimines with various unactivated alkyl halides, including alkyl iodides, alkyl bromides and alkyl chlorides, enabling the formation of chiral α-tertiary aminoesters with a high level of enantioselectivity and excellent functional group tolerance. Primary, secondary and tertiary organoelectrophiles are all tolerated in this asymmetric