99646-07-8Relevant academic research and scientific papers
GAS-PHASE ACID-INDUCED RING OPENING IN SUBSTITUTED 1,2-EPOXYCYCLOHEXANES
Crotti, Paolo,Macchia, Franco,Pizzabiocca, Adriano,Renzi, Gabriele,Speranza, Maurizio
, p. 739 - 746 (2007/10/02)
The nature and the stereoisomeric distribution of the neutral products obtained from the gas-phase attack of radiolytically formed Broensted +, CH5+, C2H5+, and t-C4H9+> and Lewis +, t-C4H9+, and CH3FCH3+> acids on several substituted 1,2-epoxycyclohexanes have been investigated under different experimental conditions.Isolation and identification of the neutral substituted products allowed us to confirm previous indications about highly regio- and stereo-selective cationic nucleophilic displacements on these substrates occuring in the gas-phase with complete inversion of the configuration at the reaction centre (the α-C atom).In some cases, extensive acid-induced isomerization became the only observable pathway.The relative extent of the competiting substitution and isomerization was found to depend on several factors, including the structural features and internal energy of the oxonium derivative of the epoxy substrate.The results obtained from the present gas-phase experiments are discussed in relation to gas-phase and solution studies.
SYNTHESIS OF 1,3-DIOL DERIVATIVES FROM STERICALLY OVERCROWDED OXIRANES. RING-OPENING REACTIONS OF 1-t-BUTYL-1,2-EPOXYCYCLOHEXANE.
Corona, Tiberio,Crotti, Paolo,Ferretti, Maria,Macchia, Franco
, p. 1607 - 1616 (2007/10/02)
The acid-catalysed ring-opening reactions of 1-t-butyl-1,2-epoxycyclohexane (1) (methanolysis, hydrolysis, and trichloroacetolysis in non-protic solvents) lead to very complex mixtures.In these reactions, in addition to the non-addition products in which the t-butyl skeleton is still present, considerable amounts of other products are formed.These compounds include 1,3-secondary addition products and other rearranged non-addition products which arise by rearrangement of the original skeleton of (1), by methyl group migration; the aldehyde (20) which is lackig both the t-butyl group and the cyclohexane skeleton is also obtained.However the opening reactions of (1) in acid media are highly regioselective, most of the reaction products arising from C-O breaking on the tertiary carbon.The structures and the configurations of all the reaction products have been well established by a study of their i.r. and n.m.r. data; however, in some cases the structures and configurations were confirmed either through unequivocal syntheses and/or chemical correlations.The stereoselectivity of the trichloroacetolysis reactions of (1) is not completely anti, even if the amounts of 1,2 adducts formed are somewhat small, and the syn/anti ratio increases with the polarity of the solvent.The results obtained were rationalized through a mechanism analogous to that previously proposed for 2-aryl- and 2-ethynyl-oxiranes in which different kinds of carbenium ion species are involved.
