Baba T, Yamamoto J, Hayashi K, Sato M, Yamanaka M, Kawabata T, Furuta T. Catalytic discrimination between formyl groups in regio- and stereoselective intramolecular cross-aldol reactions.
Chem Sci 2016;
7:3791-3797. [PMID:
30155021 PMCID:
PMC6013812 DOI:
10.1039/c5sc04594k]
[Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/18/2016] [Indexed: 11/21/2022] Open
Abstract
Catalytic discrimination between inequivalent formyl groups was achieved using an aniline-type acid-base catalyst for the regio-, diastereo-, and enantioselective intramolecular cross-aldol reactions of enolizable dials. Although l-proline gave a mixture of the regio- and stereoisomeric products in the presence of an N-containing 1,6-dial, the aniline-type catalyst afforded anti-3,4-disubstituted pyrrolidine in high regio-, and stereoselectivity beyond the background reaction, which led to the regioisomeric 2,3-disubstituted products. The mild reactivity of the aniline-type amine facilitated catalytic discrimination between the inequivalent formyl groups. Kinetic isotope effect studies and reductive amination experiments suggested that the regioselectivity was controlled under the enamine-forming steps.
Collapse