3.4- Benzodiazocines, 3,4-dihydro

The l,6-dihydro-3,4-benzodiazocine (185) was prepared from the diketone (60JOC1509). Attempted isomerization of (185) to the potentially aromatic 3,4-dihydro compound (186) was unsuccessful. 

Treatment of 6-phenyl-3,4-dihydro-l,5-benzodiazocin-2-amines 1 with alcoholic hydrogen chloride gives 2-(2-aminoethyl)-4-phenylquinazolines 2. The formation of 2 can be explained in terms of easy cleavage of the azomethine bond N(5)—C(6) followed by recyclization of the obtained intermediate to the six-membered ring. ° ... 

In contrast, 2-phenylphthalazin-2-ium-4-olate (227) with dimethyl acetylenedi-carboxylate in refluxing xylene gave dimethyl 1-0x0-10-phenyl-1,5-dihydro-2,5-imino-2H-benzazepine-3,4-dicarboxylate (228) (xylene, reflux, 12 h 80%) but in refluxing chloroform gave the isomeric dimethyl l-oxo-2-phenyl-1,2-dihydro-2,3-benzodiazocine-4,5-dicarboxylate (229) thermolysis of either product gave a third isomer, dimethyl 4-oxo-l,3a,4,8b-tetrahydroin-deno[l,2-fo]pyrazol-3,3a-dicarboxylate (230) (neat substrate, 180-190°C, 3-5 h >95%). ... 

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