An alternative route to 2H-naphtho[l,2-b]thiete and its cycloaddition products

2-(1H-Benzotriazol-1-ylmethyl)-1-naphthalenol (1) can be transformed in hig h yields to the corresponding thiol 4. Flash vacuum pyrolysis of 4 leads to 2H-naphtho[1,2-b]thiete (5). The benzotriazolyl group proved to be a good leaving group; however, a subsequent nitrogen extrusion takes place under f lash vacuum pyrolysis conditions and cyclopentadienecarbonitriles 6a,b are formed by a ring contraction (Scheme I). Cycloaddition reactions of 5 and d ienophiles or heterodienophiles yield the naphtho-condensed sulfur heterocy cles 8, 10, 12 and 14 (Scheme 2).