1.5- Diazabicyclo octane-2,6-dione

C, A-diphenyl nitrones (p-XC6H4CHN(0)Ph, X = NO2, Cl, H, Me and MeO) with N-phenylmaleimide to form 2,3,6-triaryl derivatives of l-oxa-2,6-diazabicyclo[3.3.0]octane-5,7-dione. No enthalpy of formation data are available for A-phenylmaleimide or for maleimide itself. However, it is available for the corresponding A-methyhnaleimide along with some other imides. The gas phase enthalpy of hydrogenation of this species (derived as the difference between its enthalpy of formation and that of N-methylsucc-inimide ) is 133.7 2.2 kJmoC. This value is essentially the same as for ethylene (derived as the difference between its enthalpy of formation and that of ethane) of 136.3 0.4 kJmoH. Therefore, let us assume the reaction of the above parent nitrone with ethylene to form the diphenylated isoxazolidine, shown in equation 12, has very much the same exothermicity as with A-phenylmaleimide, namely ca 82 kJmol . If so, the enthalpy of formation of 2,3-diphenylisoxazolidine would be 233 kJmol . Now, is this value plausible ... 

The Bayhs-Hillman reaction of optically pure azetidine-2,3-diones [235, 236] with methyl vinyl ketone in the presence of l,4-diazabicyclo[2.2.2]octane (DABCO) in acetonitrile at -20°C for 1 h have been reported to give functionalized allylic alcohols, having the p-lactam scaffold, in good yields (80%) and complete diastereoselectivity [237]. In terms of achieving good yields with a reasonable rate of reaction, 50 mol% of DABCO seemed to be the catalyst amount of choice for this reaction. No significant solvent effect was observed in the overall yield (Scheme 108). 

Reaction field theory with a spherical cavity, as proposed by Karlstrom [77, 78], has been applied to the calculation of the ECD spectrum of a rigid cyclic diamide, diazabicyclo[2,2,2]octane-3,6-dione, in an aqueous environment [79], In this case, the complete active space self-consistent field (CASSCF) and multiconfigurational second-order perturbation theory (CASPT2) methods were used. The qualitative shape of the solution-phase spectrum was reproduced by these reaction field calculations, although this was also approximately achieved by calculations on an isolated molecule. 

Lehn reported the synthesis and solid-state architecture of chiral 2,5-diazabicyclo[2.2.2]octane-3,6-dione. The racemic material adopted an infinite chain of alternating (+) and (-) units, whereas the single enantiomer formed a cyclic tetrameric structure (Fig. 11.14) [49]. 

In a similar reaction, the reduction of 3,7-dimethyl-l,5-diazabicyclo[3.3.0]-octane-2,6-dione (VIII/127) to the cyclooctane derivative VIII/128 (Scheme VIII/23) was nearly quantitative. 

One such epidioxypiperazinedione has been reduced to a regular pyrazine. Thus l,4-dibenzyl-2,3-dioxa-5,7-diazabicyclo[2.2.2]octane-6,8-dione (86) underwent reduction by sodium borohydride in ethanol at 20°C during 1 h to afford 3,6-dibenzyl-3,6-dihydroxy-3,6-dihydro-2,5( l//, 4//)-pyrazincdione (86a) in 65% yield, confirmed in structure by dehydration to 3,6-dibenzylidene-3,6-dihydro-2,5(1 H, 4//)-pyrazincdionc (86b).5... 

CarbocycUc Steroids.— The Torgov synthesis continues to exhibit its great versatility and was recently employed in the first synthesis of B-homo-oestrone. Condensation of the vinyl alcohol (407) and 2-methy 1-cyclopentane-l,3-dione in the presence of l,4-diazabicyclo[2,2 ]octane and cyclisation with toluene-p-sulphonic acid gave the B-homo-oestrapentaene (409) in 33 % overall yield from 3-methoxybenzosuberone. A three-stage reduction by sodium borohydride, catalytic hydrogenation, and lithium-ammonia afforded 3-methoxy-B-homo-... 

Fig. 2.1. Alternative hydrogen-bonding and crystal-packing arrangements for racemic (top) and (—) (bottom) forms of 2,5-diazabicyclo[2.2.2]octane-3,6-dione. Reproduced from Tetrahedron Lett., 35, 8157 (1994), by permission of Elsevier.

The structure and stereochemistry of the products of acetone-sensitized photoaddition of 1,3-dimethyluracil to keten diethyl acetal, t-butyl vinyl ether, and vinyl acetate have been elucidated 129 cis- and trans-fustd 8,8-diethoxy-2,4-diazabicyclo[4,2,0]octane-3,5-diones (157) and (158) are obtained in the ratio... 

A suspension of 4,4-dimethylpyrazolidine-3,5-dione in abs. tetrahydrofuran treated slowly with a soln. of methylmalonic didiloride in the above solvent, and refluxed 1 hr. 3,3,7-trimethyl-2,4,6,8-tetraoxo-l,5-diazabicyclo[3.3.0]octane. Y 88%. F. e. s. G. Zinner and D. Bose, Pharmazie 25, 309 (1970). 

C10H1 N20i,, 2,4-Diazabicyclo[4.2.0]-octane-3,5-dione-8-acetate, 40B, 245... 

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