Thermochrome Furofurane, II. Synthese und Thermolyseverhalten substituierter Spirochinolether der Naphthalinreihe

Thermochromic Furofuranes, II. — Synthesis and Thermolytic Behavior of Spiroquinole Ethers with Naphthalene Nucleus To obtain further insight into the new photochromic system 2/3 , various 3,4‐disubstituted spiroquinole ethers 7 have been synthesized by oxidation of 2‐alkyl‐4‐methoxy‐1‐naphtholes 5 via the corresponding quinone methides 6 . Unlike 7a , the ethers 7b – d did not yield dimeric quinone methides or furofuranes (type 2/3 ) on heating, but decomposed by retro‐diene reaction yielding monomeric methides 6 . The sterically hindered methides 6e, 6f are stable yellow compounds; 6c rearranged forming 12 which led to the naphthopyranes 11a/11b on further reaction with 6c .