Premium
Stereoselectivity of Destabilized Carbocations: 1‐Cyano‐2‐adamantyl and 3‐Cyano‐4‐protoadamantyl Cations
Author(s) -
Gomann Klaus,
Herpers Ekkehard,
Kirmse Wolfgang
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199810)1998:10<2245::aid-ejoc2245>3.0.co;2-w
Subject(s) - chemistry , solvolysis , carbocation , stereospecificity , stereoselectivity , medicinal chemistry , selectivity , yield (engineering) , oxygen , stereochemistry , hydroamination , chirality (physics) , intramolecular force , organic chemistry , catalysis , hydrolysis , materials science , metallurgy , nambu–jona lasinio model , chiral symmetry breaking , physics , quantum mechanics , quark
Nonracemic and 18 O‐labeled 4‐tosyloxyprotoadamantane‐4‐carbonitriles 10c , 11c were prepared. In 60 % dioxane, the exo ‐OTs isomer 10c afforded ca. 97% of 2‐tosyloxyadamantane‐1‐carbonitrile ( 14 ) with ee = 98% and with 23% equilibration of the tosylate oxygen atoms. The data point to a tight ion pair which undergoes nearly complete and stereospecific recombination. The endo ‐OTs isomer 11c underwent internal return to give endo ‐4‐tosyloxyprotoadamantane‐3‐carbonitrile ( 20 , 60% yield, 51% equilibration of the tosylate oxygen atoms), elimination (6%), and solvolysis (34%) competitively. 2‐Hydroxyadamantane‐1‐carbonitrile ( 15 ) and 4‐hydroxyprotoadamantane‐3‐carbonitrile ( exo / endo = 18 / 22 ≈ 2.8) were formed with ee ≥ 97%. According to these results, the chirality (unsymmetrical bridging) of the parent 2‐adamantyl cation is not detectably affected by 1‐CN whereas the endo selectivity of the parent 4‐protoadamantyl cation (symmetrical bridging) is eliminated by 3‐CN.