AN EFFICIENT APPROACH TO ISOINDOLO[2,1-B][2]BENZAZEPINES VIA INTRAMOLECULAR [4+2] CYCLOADDITION OF MALEIC ANHYDRIDE TO 4-ALPHA-FURYL-4-N-BENZYLAMINOBUT-1-ENES Article Zubkov F.I., Boltukhina E.V., Turchin K.F., Varlamov A.V. Tetrahedron. Vol. 60. 2004. P. 8455-8463