Synthesis of Substituted 2,3‐Dihydro‐1 H ‐2‐benzazepines and 1,2‐Dihydroisoquinolines Using an Isomerization‐Ring‐Closing Metathesis Strategy: Scope and Limitations

An isomerization‐ring‐closing metathesis (RCM) approach was used for the synthesis of substituted 2,3‐dihydro‐1 H ‐2‐benzazepines and 1,2‐dihydroisoquinolines. The 2,3‐dihydro‐1 H ‐2‐benzazepines were obtained from N ‐protected N ‐{2‐[(1 E )‐prop‐1‐en‐1‐yl]benzyl}prop‐2‐en‐1‐amines by RCM reaction. A double isomerisation reaction on the N ‐protected N ‐(2‐allylbenzyl)prop‐2‐en‐1‐amines and a subsequent RCM afforded the substituted 1,2‐dihydroisoquinolines. Finally, a selective isomerization of the allylamine group of N ‐protected N ‐(2‐allylbenzyl)prop‐2‐en‐1‐amines by [RuClH(CO)(PPh 3 ) 3 ], followed by RCM, did not afford the expected 2,5‐dihydro‐1 H ‐2‐benzazepines but afforded products resulting from deallylation and isomerization of the starting material.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)