1.5- Diazocines ring cleavage

Reductive ring cleavage of the tetrahydroimidazole 268 has been recorded with LAH in ether.Formation of the isoindolone 269 is in contrast with earlier reports in which ring expansion to the diazocine 270 was reported. ... 

Two derivatives of the fully conjugated 1,2-diazocine system 8 were reported in the past decade but in poor yields (14-20%) from the reaction of 2-methyl-7-tosylfuro[2,3-r/]pyridazine 101 with ynamines by a [2+2] cycloadditionring-expansion sequence (Equation 4). From the reaction mixture, the penta-substituted pyridine derivatives (14%) by an N-N bond cleavage of the pyridazine ring and benzofuranes, as the major products (31-34%) by a [4+2] cycloaddition-denitrogen reaction, were also isolated <1996H(43)199>. 

The spiro compound 106 underwent a Diels-Alder cycloaddition with dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate to give the condensed 1,2-diazocine 107, presumably via retrograde deazatization of the initial [4+2] cycloadduct with cleavage of the cyclobutane ring (Scheme 22) <20040L1313>. 

One of the more frequently reported routes to 1,5-diazocines involves reductive nitrogen-nitrogen bond cleavage of N.A -trimethylenepyrazoli-dines (56) to yield 57. This reaction was first reported by Wiselogle and co-workers, who reacted 2 mol of trimethylene bromide or chloride with 1 mol of hydrazine. They obtained, in addition to 56 (R = R1 = H) and pyrazolidine, the corresponding ring-opened compound 57 (R = R1 = H)... 

In what may foreshadow a versatile and general route to heavily functionalized 1,2-diazocines, as well as to many other larger-ring heterocyclic compounds, oxidative cleavage by periodate of the carbon-carbon double bond of a bicyclic pyrazolone was reported to yield 1,2,6,7-tetrahydro-l-methyl-2-phenyl-l,2-diazocin-3,4,8(5. -trione (29) (85%) (Equation (4)) cleavage of larger-ring... 

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