Synthesis and Photochromic Properties of 2H,9H-Indeno[1,2-f]- and 3H,7H-Indeno[2,1-i]- naphtho[2,1-b]pyrans

Expedient syntheses of the 3-hydroxy- and 6-hydroxy- derivatives of 11H-benzo[a]fluoren-11-one, obtained via Suzuki-Miyaura couplings are described. Reactions of these phenols with 1,1-diarylprop-2-yn-1-ols give indeno[2,1-i]- and indeno[1,2-f]- naphtho[2,1-b]pyranones respectively. The photochromic properties of these and the reduced derivatives are reported. A rationale for the pronounced hypsochromic shift in λmax of the photomerocyanine from a 2H,9H-indeno[1,2-f]naphtho[2,1-b]pyran is presented.