Subsequent Cycloaddition Reaction Research Articles

Fast microwave-assisted preparation of aryl and vinyl nitriles and the corresponding tetrazoles from organo-halides

Aryl and vinyl nitriles have been prepared in very high yields from the corresponding bromides using palladium-catalyzed reactions with microwave irradiation employed as the energy source. Furthermore, flash heating was used successfully for the conversion of these nitriles into aryl and vinyl tetrazoles by cycloaddition reactions. One-pot transformation of aryl halides directly to the aryl tetrazoles could be accomplished both in solution and on solid support. All reactions were completed in minutes rather than in hours or days as previously reported with the standard thermal heating technique. A very potent HIV-1 protease inhibitor (K(i) = 0. 56 nM), comprising two tetrazole heterocycles as carboxyl group bioisosteres, was prepared in one pot by microwave-promoted cyanation of a bromo precursor and a subsequent cycloaddition reaction. The temperature-time profiles at 13, 20, and 60 W magnetron input power in DMF are presented.

電解酸化系における疎水性反応場を用いた付加環化反応

Unstable intermediates were generated in situ by electrochemical oxidation of phenolic compounds to give varied cycloadducts with dienes or alkenes by using hydrophobic fields in the reaction system. In an aqueous medium, Diels-Alder reactions of quinones and dienes were markedly prometed in the presence of sodium dodecylsulfate (SDS). Electrochemical generation of unstable quinones and subsequent cycloaddition reactions with varied dienes were mediated by SDS micelle. These electrolytic reactions were also accomplished in a conductive lithium perchlorate/nitromethane system in which Diels-Alder reactions were highly promoted. In this non-aqueous reaction system, electrochemical generation and cycloaddition reactions of ο-quinone methides and unactivated alkenes were also successful to give chroman and spirochroman skeletons which have been proven to be difficult to yield in usual methods. The electrolysis in the lithium perchlorate/nitromethane system was further applied to the proposed biomimetic cycloaddition of ο-quinone methides and terpenes to give natural euglobal skeletons.

ChemInform Abstract: A Nitrone Cycloaddition to a 1,4‐Disubstituted‐Buta‐1,3‐diene. A Synthesis of 5‐(3‐Furyl)‐8‐methyloctahydroindolizine.

AbstractCoupling of furan‐3‐carbaldehyde (I) with trimethyl 4‐phosphonocrotonate (II) and subsequent cycloaddition reaction of the diene (III) with pyrroline 1‐oxide (IV) yield the diastereoisomeric methyl carboxylates (V).

ChemInform Abstract: A New Approach to the Synthesis of Pyrrolizines: A One‐Pot Procedure from 2H‐Pyrroles.

AbstractThe pyrrolizines (V) and (VIII) are synthesized from the 2H‐pyrrols (I) via the azomethine ylides (III) and by subsequent cycloaddition reaction with dimethyl acetylenedicarboxylate (IV) or methyl acrylate (VII).