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Synfacts 2018; 14(04): 0375
DOI: 10.1055/s-0037-1609410
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Tetrahydrofuroindoles by a Palladium-Catalyzed Asymmetric Dearomatization

Contributor(s):
Mark Lautens
,
Tamara Beisel
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
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Publication History

Publication Date:
15 March 2018 (online)

 
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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.


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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.


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