10.1021/jo9917285.s002
Ta-shue Chou
Ta-shue
Chou
Hong-Chuan Chen
Hong-Chuan
Chen
Woei-Chang Yang
Woei-Chang
Yang
Wan-Sheung Li
Wan-Sheung
Li
Ito Chao
Ito
Chao
Shwu-Jiuan Lee
Shwu-Jiuan
Lee
Type-Two Intramolecular Diels−Alder Reactions of
Pyrazolo-<i>o</i>-quinodimethanes
American Chemical Society
2000
Thermolysi
tricyclic
substitution position
pyrazolo
intramolecular
regioselectivity
isomeric series
demostrated
Diel
Pyrazolo
material
quinodimethane
sulfolene
pyrazole
acryloyloxy
extrusion
Intramolecular
thieno
dihydro
2000-08-09 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Type-Two_Intramolecular_Diels_Alder_Reactions_of_Pyrazolo-_i_o_i_-quinodimethanes/3720495
Two isomeric series of homologous <i>N</i>-(acryloyloxy)alkylated pyrazolo-3-sulfolenes <b>10a</b>−<b>c</b> and <b>18a</b>−<b>c</b>
have been efficiently synthesized from a common starting material, 4,6-dihydro-1<i>H</i>-thieno[3,4-<i>c</i>]pyrazole (<b>5</b>). Thermolysis of these fused 3-sulfolenes provides the corresponding <i>o</i>-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 <i>N</i>-substitution position of the pyrazolo-fused 3-sulfolenes, the
temperature required for the thermal extrusion of SO<sub>2</sub> and the regioselectivity of the T2-IMDA
reactions were influenced substantially.