Intramolecular [4+2] cycloaddition of furfurylsubstituted homoallylamines to allylhalides, acryloyl chloride and maleic anhydride

Acylation of 4-(furyl-2)-4-R-aminobut-1-enes and 4-R-4-furfurylaminobut-1-enes with maleic anhydride, acryloyl chloride or allylhalides provided 3-aza-10-oxatricyclo[5.2.1.01,5]decenes. The tricycles are formed via an initial amide formation followed by a stereoselective exo-IMDAF (Intramolecular Diels-Alder of Furan). In case of competing cycloaddition (for compounds possessing two furan or two dienophilic moieties) the most substituted fivemembered cycle is preferably annulated. Refluxing of 4-R-4-furfurylaminobut-1-enes in acetic anhydride led to exo-3-aza-11-oxatricyclo[6.2.1.01,6]undecenes with the pseudoequatorial substituent R-4. Treatment of 3-aza-10-oxatricyclo[5.2.1.01,5]decenes with PPA at 90−110°C promoted cyclic ether opening, aromatization and intramolecular cyclization reactions sequence to give the corresponding tetracyclic compounds — tetrahydroisoindolo[2,1-a]quinolines and tetrahydroisoindolo[2,1-b][2]benzazepines in good yields. Unusual products of ipso-substitution in aromatic ring were obtained on cyclization of N-p-R-substituted 2-allyl-4-oxo-3-aza-10-oxatricyclo[5.2.1.01,5]dec-8-enes.