19245-72-8Relevant articles and documents
On the stereochemical course of the addition of allylsilanes to aldehydes
Denmark, Scott E.,Weber, Eric J.,Almstead, Neil G.,Wolf, Larry M.
experimental part, p. 7701 - 7718 (2012/09/11)
Model compounds 3 and 5 have been studied to determine the orientation of the reacting double bonds in the transition state of the allylmetal-aldehyde addition. These models were designed to remove any intrinsic steric bias for the formation of the bicyclic products that would obfuscate a stereoelectronic contribution to the transition states. Model system 3 revealed a modest preference for the synclinal transition state, albeit in very low yields. Model system 5 underwent selective and largely Lewis acid independent cyclization primarily via a synclinal transition state. The high proximal selectivity observed in these cyclizations likely reflects the selectivity of an unhindered allylmetal-aldehyde addition for the synclinal transition state and results from a stereoelectronic preference, not an intrinsic steric bias, for the synclinal arrangement of double bonds.
Syntheses with organoboranes. IX. Vinyl- and 1-alkenyldichloroboranes as ethylene and 1-alkene equivalents for the Diels-Alder reaction
Zaidlewicz, Marek,Binkul, Jacek R.,Sokol, Wojciech
, p. 354 - 362 (2007/10/03)
Vinyl- and 1-alkenyldichloroboranes were used as dienophiles for the Diels-Alder reaction with representative aliphatic and cyclic 1,3-dienes. The organoborane adducts were transformed into the corresponding olefins either by protonolysis or by oxidation-mesylation-reduction. Direct protonolysis of the adducts gave in most cases mixtures of olefins whereas the reduction of mesylates with lithium triethylborohydride produced pure olefins in good yields.
Ouverture acidocatalysee d'epoxydes bicyclooctaniques: Intervention d'un mecanisme A2 avec retention de configuration
Plenat, Francoise,Renard, Gilbert,Christol, Henri
, p. 125 - 132 (2007/10/02)
During the stereochemical study of the products obtained by acid-catalysed ring opening of 2,3-endo epoxynorbornane, a concerted "front" attack mechanism has been brought to light.This can be explained by the known preference for intramolecular rather than intermolecular mechanisms.This acid-catalyzed ring opening has been extended to 2,3-epoxybicyclooctane, the bonds of which are in the same spatial position towards the epoxy carbon atoms and which can undergo anti and "front" attack of the epoxide ring.Products arising from both kinds of intramolecular attack can be isolated.In addition, the ring opening reaction of 2,3-endo and exo epoxy-5,6-trans-dicarbomethoxybicyclooctanes indicates that they proceed by a concerted mechanism, so that the "front" attack mechanism must be specially favourable to these bicyclic structures.Since the reactions considered are like bimolecular nucleophilic substitutions, for which the anti attack mechanism is known to be energetically favoured over the "front" attack, the following suggestions can be made to explain our results: there is steric hindrance to anti approach of the external nucleophile, torsional strain lowering and favourable orbital alignment for the "front" attack.
