Journal of the American Chemical Society p. 1598 - 1605 (1986)
Update date:2022-07-30
Topics:
Cheung, C. K.
Tseng, L. T
Lin, M.-H.
Srivastava, S.
Noble, W. J.
The argument is developed that 2,5-(or 1,4-) substituted adamantanes are the geometric equivalents of enatiomers in that stereorandom reactions at the 2-position would be revealed by a 50/50 product composition.Systematic and fairly large deviations from this expectation are encountered in nucleophilic additions to the carbonyl group of 5-substituted adamantanones; electron-withdrawing substituents favor syn approach, and electron-donating groups lead to anti approach.The product distribution correlates well with the strength of the induction: Δρ = -0.39.These findings lend strong support to Cieplak's view of electronic effects in asymmetric induction, which attributes these effects to preferential interaction of the newly developing ?* orbital with the electron-richest anti-periplanar bonds.The equivalence objective is achieved with 5-deuterio substitution, the isomers being distinguishable by 13C (and sometimes 2H) NMR spectroscopy.This probe is then applied to determine the stereochemistry of solvolysis of 2-adamantyl substrates; predominanat retention is found.Large 5-substituent effects are also described in the capture of both tertiary and secondary 2-adamantyl cations.The tertiary ions produce the same mixtures regardless of progenitor; the now very large deviations from 50/50 product distributions are again attributed to the Cieplak effect that for cations translates into ? participation.Thus, the 5-substituted tertiary 2-adamantyl cations constitute an exceedingly sensitive indicator of ? participation; no alternative interpretation is available.Secondary ions, generated from the alcohol and capture with Lucas reagent, give rise to products of largely retained configuration, more so for the Z than for the E isomers as expected.The retention in the secondary ions is almost certainly related to now stronger participation and hence more strongly ?-delocalized ions, but in this case, pyramidal cations or loose ion pairs may also contribute.
View MoreJiangxi Lanqi Fine Chemical S&T Co., Ltd.
Contact:+86-21-64891143
Address:XinJiShan Industrial Area, Zhangshu City, JiangXi Province, China
Tianjin Te-An Chemtech Co., Ltd.(expird)
Contact:+86-22-65378638
Address:A5-8, No.80 Haiyun Street, TEDA
Junkai (Tianjin) Chemical Co., Ltd.
website:http://www.junkaichem.com
Contact:86-22-85689515
Address:Room 8-501, Building K2, The Hi-Tech Green Industrial Base, No.6, 6th Road, Hi-Tech Development Road, Tianjin Hi-Tech IndustrialPark, Tianjin, China.
Xinjiang Zhongtai Chemical Co., Ltd.
Contact:+86-991-8788172
Address:NO.78 XISHAN RD.URUMQI,CHINA
Xian Changyue Biological Technology Co., Ltd.
website:https://www.xachangyue.com/
Contact:+86-029-62886900
Address:Keji Road NO.70
Doi:10.1016/j.bmcl.2007.09.022
(2007)Doi:10.1021/ja01604a064
(1956)Doi:10.1016/j.tetlet.2007.09.144
(2007)Doi:10.1039/b713107k
(2007)Doi:10.1021/jo7015967
(2007)Doi:10.1055/s-0030-1260066
(2011)