Facile one-pot synthesis of photochromic pyrans.

[reaction: see text]. Photochromic pyrans, including [3H]naphtho[2,1-b]pyrans, [2H]naphtho[1,2-b]pyrans, indeno-fused naphtho[1,2-b]pyrans, and heteroannulated pyrans, were synthesized in excellent yields through a facile one-pot procedure by reaction of propargyl alcohol and naphthol or phenol derivatives in the presence of 5 mol % PPTS and 2 equiv of (MeO)3CH. Symmetrical and nonsymmetrical bispyrans can also be prepared using the protocol.