Cheng Q.
Zhang F.
Cai Y.
Guo Y.-L.
*
You S.-L.
* Shanghai Institute of Organic Chemistry and Collaborative Innovation Center of Chemical
Science and Engineering, Tianjin, R. P. of China
Stereodivergent Synthesis of Tetrahydrofuroindoles through Pd-Catalyzed Asymmetric
Dearomative Formal [3+2] Cycloaddition.
Angew. Chem. Int. Ed. 2018;
57: 2134-2138
Key words
palladium catalysis - catalytic asymmetric dearomatization - [3+2] cycloaddition -
tetrahydrofuro-indoles
Significance
The authors developed a palladium-catalyzed diastereoselective and enantioselective
dearomative formal [3+2] cycloaddition for the synthesis of tetrahydrofuroindoles.
Remarkably, the polarity of the solvent was found to play a key role in the diastereoselectivity.
Compared with toluene, the reactions in acetonitrile occurred faster and produced
the reversed diastereoisomer with higher enantioselectivity.
Comment
Mechanistic studies were conducted to illustrate the origin of the diastereodivergency.
The kinetic experiments indicate that the reactions in different solvents proceed
by the same pathway with different rate-limiting steps, thereby leading to a reversed
stereocontrol. ESI-MS experiments support the existence of key palladium complex intermediates
and the proposed catalytic cycle. Several transformations of one of the products were
also demonstrated.
