TY - JOUR
T1 - Influence of electron donating aromatic substituents on the stereochemistry of the products in cycloalkylations of 2-(2-arylethyl)-3,3-dimethyl-1- methylene-cyclohexane and related substrates
T2 - Mechanisms of aromatic cycloalkylations
AU - Ghosh, Sukumar
AU - Banik, Bimal K.
AU - Ghatak, Usha Ranjan
PY - 1991
Y1 - 1991
N2 - The critical role of the aromatic ring substituents in open chain substrates, in acid-catalysed aromatic cycloalkylations with an unsubstituted and a few isomeric mono- and di-methoxy substituted 2-(2-arylethyl)-3,3- dimethyl-1-methylenecyclohexanes 8a-d,h-j and two isomeric 2-(2-dimethoxy- phenylethyl)-1,3,3-trimethylcyclohexanols 5i,j, in determining the distributions of the respective trans- and cis-podocarpa-8,11,13-trienes, has been investigated and the results have been analysed. Olefin or alcohol precursors, having unactivated aromatic rings, proceed with high stereoselectivity via attack of the aromatic ring on a conformationally preferred cyclohexyl cation leading to the respective trans-products, while in substrates with an electron donating aromatic substituent para to the site of electrophilic attack, proceed directly in the exocyclic olefin or through the intervention of cyclohexenyl intermediates forming substantial amounts of the corresponding cis-products, in addition to the trans-products involving cyclohexyl cations.
AB - The critical role of the aromatic ring substituents in open chain substrates, in acid-catalysed aromatic cycloalkylations with an unsubstituted and a few isomeric mono- and di-methoxy substituted 2-(2-arylethyl)-3,3- dimethyl-1-methylenecyclohexanes 8a-d,h-j and two isomeric 2-(2-dimethoxy- phenylethyl)-1,3,3-trimethylcyclohexanols 5i,j, in determining the distributions of the respective trans- and cis-podocarpa-8,11,13-trienes, has been investigated and the results have been analysed. Olefin or alcohol precursors, having unactivated aromatic rings, proceed with high stereoselectivity via attack of the aromatic ring on a conformationally preferred cyclohexyl cation leading to the respective trans-products, while in substrates with an electron donating aromatic substituent para to the site of electrophilic attack, proceed directly in the exocyclic olefin or through the intervention of cyclohexenyl intermediates forming substantial amounts of the corresponding cis-products, in addition to the trans-products involving cyclohexyl cations.
UR - http://www.scopus.com/inward/record.url?scp=37049083147&partnerID=8YFLogxK
U2 - 10.1039/p19910003189
DO - 10.1039/p19910003189
M3 - Artículo
SN - 1472-7781
SP - 3189
EP - 3193
JO - Journal of the Chemical Society, Perkin Transactions 1
JF - Journal of the Chemical Society, Perkin Transactions 1
IS - 12
ER -