Rhodium‐Catalyzed Enantioselective [4+2] Cycloadditions of Vinylcarbenes with Dienes
作者:Bowen Zhang、Huw M. L. Davies
DOI:10.1002/anie.201914354
日期:2020.3.16
The reaction of 2-siloxycyclo-1,3-dienes with E-vinyldiazoacetates in the presence of the bulky chiral dirhodium tetracarboxylate catalyst, Rh2 (R-p-PhTPCP)4 results in an enantioselective [4+2] cycloaddition, in which three new stereogenic centers are formed. The [4+2] cycloadducts are generated as single diastereomers with high enantiocontrol (95-98 % ee). When the diene contains an additional stereogenic
Access to α-Pyrazole and α-Triazole Derivatives of Ketones from Oxidative Heteroarylation of Silyl Enolethers
作者:Sandeep Dhanju、Aidan C. Caravana、Regan J. Thomson
DOI:10.1021/acs.orglett.0c03005
日期:2020.10.16
The synthesis of α-pyrazole and α-triazole derivatives of ketones by the ceric ammonium nitrate-mediated oxidative coupling of enolsilanes with heteroarenes is reported. The reaction proceeds under mild reaction conditions to provide a diversity of products, including sterically hindered fully substituted derivatives.
A chiral probe for the asynchronous transition state of diels-alder reactions with acetylenedicarboxylate
作者:Ronald N. Buckle、D.Jean Burnell
DOI:10.1016/s0040-4020(99)00982-5
日期:1999.12
Diels-Alderreactions took place with modest diastereoselectivity between dimethylcyclo-hexadiene derivative 3a and di-(−)-menthyl acetylenedicarboxylate, whereas the dimethylcyclohexadiene 2 showed no selectivity whatsoever. These results can be rationalized in terms of a complete lack of any endo-exo preference for the carboxylate groups and a more synchronous addition with 3a than with 2.
Nucleophilic substitution gone awry: A novel cyclopropanation reaction with a surprising stereochemical outcome
作者:Charles J. Torborg、John J. Rabasco、Steven R. Kass
DOI:10.1016/0040-4039(95)01192-k
日期:1995.8
triisopropylbenzene sulfonate ester of 2-methoxy-5,5-dimethyl-2-vinyl-3-cyclohexen-1-ol (1) to afford 8-methoxy-6,6-dimethylspiro[2.5]oct-4-ene (3). Labeling studies reveal that this novel cyclopropane forming reaction proceeds with retention of configuration at the newly formed quaternary center.