Refernces
10.3987/com-95-7257
The research aimed to develop an efficient synthetic approach to the decalin unit, which is a key intermediate for the synthesis of compactin, a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and an effective hypocholesterolemic agent. The study focused on the microwave-accelerated intramolecular Diels-Alder reaction of substrates 5a-c, which were prepared from 3-ethoxy-2-cyclohexenone. The reaction involved the use of vinylmagnesium bromide, hydrochloric acid, lithium aluminum hydride, ethyl hydrogen malate, ethyl hydrogen fumarate, and BuLi with maleic anhydride. The researchers found that microwave irradiation significantly accelerated the reaction compared to conventional heating, leading to the formation of the desired exo adduct (7c) with high stereoselectivity. The resulting 7c was then converted to the decalin unit (2a) through a series of chemical reactions, thus accomplishing an effective synthesis of the decalin unit required for an approach to compactin.
10.1021/jo00384a049
The research focuses on the thermal rearrangement of the trans-trimethylenenorbornene derivative 3 to the tricyclodecene 4. The purpose of the study is to elucidate the energetics of this remarkable process, which occurs at relatively low temperatures and yields a single product, and to reexamine the mechanism of 1,3-sigmatropic migrations in such systems under more favorable experimental conditions. The key chemicals used in the research include the trans-trimethylenenorbornene derivative 3, decalin as the solvent for the kinetic studies, and various reagents for the molecular mechanics calculations. The conclusions drawn from the research indicate that the rearrangement of 3 is highly stereospecific and exothermic, with an activation energy determined from kinetic studies and enthalpies of reaction calculated using molecular mechanics. The results support a concerted mechanism for the rearrangement, as opposed to a diradical pathway, based on the high stereospecificity observed and the molecular mechanics calculations.
10.1016/0040-4020(82)80160-9
The research focused on determining the activation energy for the ring-closure reaction of ground state triplet trimethylenemethane (I) to methylenecyclopropane. The purpose was to measure this energy by monitoring the rate of disappearance of the electron spin resonance spectrum over a specific temperature range in frozen solid matrices, using 3-methylenecyclobutanone and methylenecyclopropane as precursors to trimethylenemethane. The study concluded that the activation energy for the ring-closure was significantly lower than the theoretical estimates, with a value of 7 kcal/mole, contrasting with the approximate 20 kcal/mole barrier suggested by theoretical models. The chemicals used in the process included 3-methylenecyclobutanone, methylenecyclopropane, isobutylene, and various solvents such as methylcyclohexane, perfluoromethylcyclohexane, decalin, and tetrahydrofuran for the matrix solutions. The research also involved the synthesis and use of fully deuterated methylenecyclopropane-da to investigate the possibility of a tunneling mechanism in the ring-closure reaction.
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