Diastereo- and enantioselective N-heterocyclic carbene catalyzed 1-azadiene Diels-Alder reactions of (E)-2-styrylbenzothiazoles with alpha-chloro aldehydes are reported. This annulation strategy provides an efficient access to medicinally important dihydrobenzothiazolopyridin-1-ones in good to excellent yields (44-97%) with very good to excellent stereoselectivities (up to 9: 1 dr, 98% ee) and tolerates quite a range of substituents.
Sakamoto Masanori, Nozaka Asae, Shimamoto Mino, Ozaki Hideki, Suzuki Yoko+, Chem. and Pharm. Bull, 42 (1994) N 6, S 1367-1369