Torquoselective 6p-electron electrocyclic ring-closure of 1-azatrienes containing chirality at the C-terminus

ORGN 371

Nadiya Sydorenko, sydorenko@wisc.edu, Division of Pharmaceutical Sciences and Department of Chemistry, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705-2222 and Richard P. Hsung, rphsung@pharmacy.wisc.edu, Division of Pharmaceutical Sciences and Department of Chemistry, University of Wisconsin-Madison, 777 Highland Ave., Rennebohm Hall, Madison, WI 53705-2222.
An aza-[3 + 3] annulation reaction represents a very useful synthetic strategy for construction of various heterocyclic systems and related alkaloids. It also provides a unique opportunity to develop approaches toward a stereoselective pericyclic ring-closure of intermediate 1-azatrienes, leading to chiral 1,2-dihydropyridines. Herein, we report torquoselective pericyclic ring-closures of 1-azatrienes, a key step in the aza-[3 + 3] annulation. Chiral vinyl iminium ions 1 were employed to generate 1-azatrienes 3 possessing chirality at the C-terminus. Cycloadducts 4 were efficiently formed with up to 9 : 1 diastereomeric ratios. The level of stereochemical induction depends upon both rotational preferences during the ring-closure and relative stabilities of the [3 + 3] cycloadducts.

 

New Reactions and Methodology
8:00 AM-12:00 PM, Tuesday, 12 September 2006 Moscone Center -- Room 133, Oral

Division of Organic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006