%0 Journal Article %A Chou, Ta-shue %A Chen, Hong-Chuan %A Yang, Woei-Chang %A Li, Wan-Sheung %A Chao, Ito %A Lee, Shwu-Jiuan %D 2000 %T Type-Two Intramolecular Diels−Alder Reactions of Pyrazolo-o-quinodimethanes %U https://acs.figshare.com/articles/journal_contribution/Type-Two_Intramolecular_Diels_Alder_Reactions_of_Pyrazolo-_i_o_i_-quinodimethanes/3720495 %R 10.1021/jo9917285.s002 %2 https://ndownloader.figshare.com/files/5812191 %K Thermolysi %K tricyclic %K substitution position %K pyrazolo %K intramolecular %K regioselectivity %K isomeric series %K demostrated %K Diel %K Pyrazolo %K material %K quinodimethane %K sulfolene %K pyrazole %K acryloyloxy %K extrusion %K Intramolecular %K thieno %K dihydro %X Two isomeric series of homologous N-(acryloyloxy)alkylated pyrazolo-3-sulfolenes 10ac and 18ac have been efficiently synthesized from a common starting material, 4,6-dihydro-1H-thieno[3,4-c]pyrazole (5). Thermolysis of these fused 3-sulfolenes provides the corresponding o-quinodimethanes which simultaneously undergo “type-two” intramolecular Diels−Alder reactions to form two- and three-atom-bridged tricyclic pyrazoles which are otherwise difficult to prepare. It was also demostrated that, depending on the N-substitution position of the pyrazolo-fused 3-sulfolenes, the temperature required for the thermal extrusion of SO2 and the regioselectivity of the T2-IMDA reactions were influenced substantially. %I ACS Publications