ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

E-mail: xqyu@tfol.com

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.

DOI: 10.2478/s11696-008-0010-6

Chemical Papers 62 (2) 187–193 (2008)