317801-56-2Relevant articles and documents
Synthesis of 3-methylenecyclohexan-1-ols by lewis acid catalyzed cyclization of (epoxy-allyl)silanes
Pulido, Francisco J.,Barbero, Asuncion,Castrenoa, Pilar
experimental part, p. 1307 - 1313 (2010/04/29)
A new route for the synthesis of (epoxy-allyl)silanes bearing the PhMe 2Si group has been developed and their acid-catalyzed cyclization studied. The so-called normal products derived from 5-exo or 6-endo attack were never obtained. On the contrary, an interesting tandem rearrangement/cyclization process was observed, which selectively led to 3-methylenecyclohexan-1-ols. A mechanism is proposed to explain this tandem reaction. The stereoselectivity of the cyclization process depends on the nature of the catalyst.
Asymmetric synthesis and Lewis acid mediated type II carbonyl ene cyclisations of (R)-2-isopropyl-5-methylhex-5-enal
Braddock, D. Christopher,Brown, John M.
, p. 3591 - 3607 (2007/10/03)
The asymmetric synthesis of (R)-2-isopropyl-5-methylhex-5-enal in 98% ee is described. It was discovered that the key alkylation step employing an Evans chiral auxiliary and 3-methylbut-3-en-1-yl trifluoromethanesulphonate as the alkylating agent led to significant competing O-alkylation, a phenomenon not previously reported. Type II carbonyl ene cyclisation of the aldehyde with a range of Lewis acids led to either the (R,R)- or (R,S)-5-methylidenecyclohexanols without concurrent racemisation of the alpha stereogenic centre of the aldehyde. Conditions for effecting the easy racemisation of a model enantiomerically pure aldehyde, (S)-2-methylbutanal, were developed. In an effort to secure a dynamic kinetic resolution procedure, these conditions were applied to (R)-2-isopropyl-5-methylhex-5-enal. However, a competing and dominant Prins cyclisation occurred instead leading to a mixture of all possible cycloadducts, all of which were obtained in 98% ee. Any unreacted aldehyde was found to be enantiomerically pure. Copyright (C) 2000 Elsevier Science Ltd.
Unprecedented stereochemical control in the intramolecular ene-reactions of δ,ε-unsaturated aldehydes using exceptionally bulky organoaluminum reagents: Elucidation of the transition state
Ooi,Maruoka,Yamamoto
, p. 6505 - 6522 (2007/10/02)
Unprecendented stereochemical control has been achieved in the type II intramolecular ene reactions of δ,ε-unsaturated aldehydes leading to trans-cyclohexanols with excellent selectivity under very mild conditions, using exceptionally bulky methylaluminum bis(4-bromo-2,6-di-tert-butylphenoxide) (MABR). Success of the stereocontrolled cyclization can be ascribable to the ability of this modified organoaluminum reagents, MABR, to change the conformation of the transition state. Examining the ene reactions of substrates 7, 11, 14 with MABR, the stereochemical outcome of the present organoaluminum-promoted intramolecular ene reactions is further elucidated.
