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Statistical models for the study of solvent effects on the endo/exo selectivity of Diels-Alder reactions using molecular surface electrostatic potentials was obtained. The models show that hydrogen bond interactions of solvent molecules favor the predominance of the endo isomer for the reaction of methyl acrylate, methyl methacrylate and methyl trans-crotonate with cyclopentadiene whereas the effect of solvophobicity seems to be negligible. © 2003 Published by Elsevier Ltd  

In this article, we report the computational examination of the impact of hydrogen bonding (HB) on the stereoselectivity of a series of Diels-Alder (DA) reactions. Four different types of diene/dienophile couples were studied including (a) cyclopenta-2,4-dien-1-ol and heteroatom-substituted cyclopentenes, (b) substituted cyclopentadienes andN-protonated 2,5-dihydro-1H-pyrrole, (c) furan andN-protonated 5-azabicyclo[2.1.1]hex-2-ene, and (d)N-protonated cyclopenta-2,4-dien-1-amine and α,β-unsaturated carbonyl compounds. These systems were designed such that the HB can only exist in theexoreaction pathway. The optimized structures of the transition states (TSs) and products, along with the... 

A novel and efficient multicomponent reaction for the synthesis of polysubstituted pyrrolidine derivatives is described under catalyst-free conditions using ultrasonic irradiation. The reactions were performed via a one-pot four-component condensation of secondary amines, carbon disulfide, isocyanides, and gem-dicyano olefins at room temperature to afford polysubstituted pyrrolidines diastereoselectively in 56-96% yields. This is the first report of a Mumm-type rearrangement with dithiocarbamates followed by intramolecular cyclization, which leads to the preparation of the key structure of pyrrolidine. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche... 

Herein, functionalized spiro[indoline-3,5′-pyrazolo[1,2-a]pyridazine]-7′-carbonitrile containing two contiguous chiral stereocenters was efficiently synthesized in a satisfactory yield (up to 91% yield) and with excellent diastereoselectivity. We have reached this satisfactory yield by DABCO-catalyzed [3+3] annulation reactions of an isatin N,N′-cyclic azomethine imine 1,3-dipole with a Knoevenagel intermediate in dichloromethane (DCM) as solvent at ambient temperature; this was an entirely new strategy for creating one quaternary stereogenic center at the position-3 of an oxindole structure using an abnormal tandem Michael addition, N-cyclization, and a unique approach via the azomethine... 

Herein, functionalized spiro[indoline-3,5′-pyrazolo[1,2-a]pyridazine]-7′-carbonitrile containing two contiguous chiral stereocenters was efficiently synthesized in a satisfactory yield (up to 91% yield) and with excellent diastereoselectivity. We have reached this satisfactory yield by DABCO-catalyzed [3+3] annulation reactions of an isatin N,N′-cyclic azomethine imine 1,3-dipole with a Knoevenagel intermediate in dichloromethane (DCM) as solvent at ambient temperature; this was an entirely new strategy for creating one quaternary stereogenic center at the position-3 of an oxindole structure using an abnormal tandem Michael addition, N-cyclization, and a unique approach via the azomethine...