2H-Azirines from a Concerted Addition of Alkylcarbenes to Nitrile Groups
摘要:
Photolysis of aziadamantanos in the presence of fumoronitrile (FN) unexpectedly afforded conjugated 2H-azirines resulting from addition of the carbene to the CN triple bond. This represents the first example of a direct azirine formation starting from an alkylcarbene for which a concerted pathway is postulated. The novel outcome if the reaction is favored by the prior formation of a carbene-alkene complex, a type of adduct that only recently has been described.
Reversal of Diastereoselectivities in Intra- and Intermolecular Reactions of 2-Adamantanylidenes Primarily Caused by Electron-Donating and Electron- Withdrawing Substituents on C5
作者:Wolfgang Knoll、Michael M. Bobek、Hermann Kalchhauser、Murray G. Rosenberg、Udo H. Brinker
DOI:10.1021/ol0350700
日期:2003.8.1
A reversal of diastereoselectivity was observed for novel 5-(trimethylsilyl)adamantan-2-ylidene (1c) with regard to 5-hydroxyadamantan-2-ylidene (1a). Ostensibly in intermolecular reactions, 5-substituted 2-adamantanylidenes (1) are sterically unbiased. However, inductive effects originating from the pendant group bend the divalent carbon bridge of 1 either toward (ERG's, e.g., -Si(CH3)(3)) or away from (EWG's, e.g., -OH) the gamma-position. Hence, the more exposed side is more susceptible to intermolecular reaction and the other side concomitantly undergoes intramolecular 1,3-CH insertions more readily.
4-Aziadamantan-1-amine: synthesis, reactions and cyclodextrin complexes
作者:Wolfgang Knoll、Michael M Bobek、Gerald Giester、Udo H Brinker
DOI:10.1016/s0040-4039(01)02013-5
日期:2001.12
A new and potentially therapeutic diazirine, 4-aziadamantan-1-amine, was synthesized. Structural characterization also included single crystal X-ray diffraction analysis. Photolysis of the title Compound in the solid phase afforded an azine. In contrast. pyrolysis in the gas phase gave two intramolecular carbene insertion products in a 4:1 ratio. A rationale for the observed diastereoselectivity is offered based upon ab initio calculations. Finally, inclusion compounds of the title compound with alpha- and beta -cyclodextrin were prepared. A 2:1 complex bearing two hosts was formed with alpha -cyclodextrin and a 1:1 complex was obtained with beta -cyclodextrin. The association constants were determined via induced circular dichroism (ICD) analysis. (C), 2001 Elsevier Science Ltd. All rights reserved.