3‐Alkyl‐1‐benzoxepin‐5‐on‐Derivate und 2‐Alkyl‐1, 4‐naphthochinone aus 2‐Acylaryl‐propargyläthern

Abstract

3‐Alkyl‐1‐benzoxepin‐5‐one derivatives and 2‐alkyl‐1,4‐naphtoquinones from 2‐acylaryl propargyl ethers.It was found that 3‐alkyl‐1‐benzoxepin‐5(2H)‐ones of type B can be synthesized by treating 2‐acylaryl propargyl ethers of type A with sodium methylsulfinyl methide (NaMSM, dimesyl sodium) (Scheme 13). Oxepinone derivatives of type B undergo ring contraction with base (also NaMSM) to yield the quinol derivatives C which, oxidize (during work‐up), if R2 = H, to the 1,4‐naphthoquinones D (Scheme 13).The propargyl ethers used are listed in Scheme 1. The naphthalene derivatives 1 and 3 give oxepinones (E‐9 and a mixture of 14/15 respectively), whereas the expected oxepinone from 2 is transformed directly into the quinone 11 (Scheme 2, 3 and 5). Isomerizations of 2‐acetylphenyl propargyl ethers (4, 5 and 6) (Schemes 6, 7 and 8) are less successful because of side reactions. If however the acetyl group is replaced by a propionyl or substituted propionyl group (as in ethers 7 and 8) oxepinones are obtained again in good yield (Scheme 9).The mechanistic pathway for the transformation of naphthyl propargyl ethers (and phenyl derivatives) under influence of NaMSM is shown in Scheme 10. The base‐catalysed conversion of 4‐phenyl‐l‐benzoxepin‐5(2H)‐one,benzo[f]furo[2,3‐c](10 H)‐oxepin‐4‐oncsand 3‐methoxy‐G,11‐ dihydro‐dibenzo[b, e]loxepin‐11‐oneinto thc corresponding quinones has been reported [13] [20] [21].The conversion of 2‐acylaryl propargyl others via the isolable benzoxepin‐5‐one derivativcs or directly into the specifically substituted 1,4‐naphthoquinone derivatives is of synthetic interest.