Giovanni Ingrosso

Kinetic resolution by epoxide hydrolase catalyzed hydrolysis of racemic methyl substituted methylenecyclohexene oxides

Abstract A complete kinetic resolution of 2,2-dimethylmethylenecyclohexene oxide and a partial resolution of the cis and trans -2-methylmethylenecyclohexene oxides, but not of their 3-methyl substituted isomers, have been achieved by partial hydrolysis to the corresponding diols using the microsomal epoxide hydrolase. No substrate enantioselectivity was in found for the hydrolysis of all these substrates by the cytosolic epoxide hydrolase.

The steric course of the reaction of ethylene oxide with hydrogen halides in the gas phase

The steric course of the gas-phase reaction of trans-[2H2]ethylene oxide with HF, HCl, and HBr was investigated in order to test experimentally a mechanistic proposal based on ab initio calculations involving a concerted syn-opening mechanism. In contrast with this proposal the reactions with HCl and HBr take place entirely with anti-opening of the ring to give erythro-2-chloro- and 2-bromo[1,2-2H2]ethanol. The reaction of ethylene oxide with gaseous HF yields only 5% 2-fluoroethanol, 37% dioxan, oligomers and polymers being the main products. An improved method for the conversion of cis- and trans-[2H2]ethylene into the corresponding epoxides is described.

Influence of substituents in the 3-position of cyclohexene oxides on the rates of their reactions with hydrogen chloride in low polarity aprotic solvents

Rates of reactions of cyclohexene oxide and of its cis- and trans-3-methyl and 3-t-butyl derivatives with HCl were measured in toluene and CCl4 by a calorimetric method. Although these rates are very sensitive to trace impurities, satisfactory second-order kinetics were obtained in the presence of small amounts of water or tetrahydrofuran. An equatorial substituent in the 3-position trans to the epoxide oxygen has a rate-retarding effect which is larger for t-butyl than for methyl. The qualitative agreement between the ratios of the rates of formation of the four trans-chlorohydrins from each cis–trans pair of the 3-alkylcyclohexene oxides and the molar ratios of the bromohydrins obtained in the reactions of the corresponding alkylcyclohexenes with NBS in DMSO–water supports the hypothesis that in the latter reaction the nucleophillic step, rather than the electrophilic one, is rate determining.