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Most Requested Journal Articles 4Q07-Chemistry and Related Science

Following is one of the journal articles most requested by researchers using CAS electronic products.

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CAS indexed 67 chemical substances from this document. CAS subject entries for this document include: Density functional theory; Functional groups; Imines; and 12 additional concepts

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TITLE:	Chiral Bronsted Acid Catalyzed Enantioselective Mannich-Type Reaction
AUTHOR(S):	Yamanaka, Masahiro; Itoh, Junji; Fuchibe, Kohei; Akiyama, Takahiko
CORPORATE SOURCE:	Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
SOURCE:	Journal of the American Chemical Society (2007), 129(21), 6756-6764 CODEN: JACSAT; ISSN: 0002-7863
PUBLISHER:	American Chemical Society
LANGUAGE:	English

ABSTRACT:
Mannich-type reaction of ketene silyl acetals with aldimines proceeded catalytically by a phosphoric acid diester, derived from (R)-BINOL, as a chiral Broensted acid to afford .beta.-amino esters with good diastereoselectivity in favor of the syn isomer and high enantioselectivity (up to 96% ee). The highest enantioselectivity was achieved by the phosphoric acid diester bearing 4-nitrophenyl groups on the 3,3'-positions of BINOL. The N-2-hydroxyphenyl group of aldimine is essential for the present Mannich-type reaction. In combination with these exptl. studies, two possible monocoordination and dicoordination pathways were explored using d. functional theory calcns. (BHandHLYP/6-31G*). The present reaction proceeds via a dicoordination pathway through the zwitterionic and nine-membered cyclic transition state (TS) consisting of the aldimine and the phosphoric acid. The re-facial selectivity was also well-rationalized theor. The nine-membered cyclic structure and arom. stacking interaction between the 4-nitrophenyl group and N-aryl group would fix the geometry of aldimine on the transition state, and the si-facial attacking TS is less favored by the steric hindrance of the 3,3'-aryl substituents.