ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Asymmetric synthesis of 2,6-substituted dihydropyrone catalyzed by 3-monosubstituted and 3,3′-bisubstituted BINOL titanium complexes
Hong Yu, Ji Zhang, Yuan-Cong Zhao, Na Wang, Qin Wang, Xin-Bin Yang, and Xiao-Qi Yu
Department of Chemistry, Key Laboratory of Green Chemistry and Technology (Ministry of Education), Sichuan University, Chengdu, Sichuan, 610064, China
Received: 31 March 2007 Revised: 15 July 2007 Accepted: 19 July 2007
Abstract: Asymmetric hetero-Diels-Alder (HDA) reactions of aromatic aldehydes with Danishefsky’s diene derivative were carried out smoothly
in the presence of the Ti(IV)-(R)-BINOL (1:1.2) complex to give the corresponding chiral 2,6-disubstituted dihydropyrones under mild conditions. The readily
accessible I-Ti(OCH(CH3)2)4 (1.2:1) complex was found to be an effective catalyst for this reaction. Aromatic aldehydes afforded the corresponding products
in moderate yields (up to 72 %) with good enantioselectivities (up to 80 % ee). Aromatic aldehydes in presence of the TiCl4-NaOCH3-II (1:4.2:1.2) complex gave the products in higher yields (up to 73 %) with better enantioseletivities (up to 84 % ee).
Keywords: hetero-Diels-Alder reaction - BINOL - asymmetric catalysis - dihydropyrone
Full paper is available at www.springerlink.com.
Chemical Papers 62 (2) 187–193 (2008)
Wednesday, September 22, 2021