The influence of electronic factors on Pd-mediated cycloisomerization: a systematic investigation of competitive 6-exo-dig versus 7-endo-dig cyclizations of sugar alkynols
作者:C.V. Ramana、Boddeti Induvadana、Burgula Srinivas、Kommagalla Yadagiri、Madhusudhan N. Deshmukh、Rajesh G. Gonnade
DOI:10.1016/j.tet.2009.09.071
日期:2009.11
Pd-mediated cycloisomerization of 3-C-propargyl-ribo- and allofuranose derivatives was investigated in detail to understand the influence of electronic factors on the regioselectivity (6-exo- vs 7-endo) of alkynol cycloisomerization leading either to a six- or seven-membered ring. In general, the 6-exo-dig mode of cyclization is facile and is independent of electronic factors. With some of the alkynols
的钯-介导的环异构3- Ç -propargyl-核糖-和异体呋喃糖衍生物进行了详细的调查,以了解的电子因素对区域选择性的影响(6-外型- VS -7-内)炔醇环异构导致要么到六的或七元环。通常,环化反应的6- exo- dig模式很容易,并且与电子因素无关。对于某些炔醇,观察到炔单元的区域选择性(7-内酰胺化)水合,这归因于C(3)-OH的参与。当C(3)-OH被保护为苄醚,这些炔醇的环异构化仅以6-外-dig方式发生,从而导致相应的[3.2.1]-双环缩酮。进行的其他对照实验均支持C(3)-OH参与区域选择性炔烃水合作用。