Triazolinediones synthesis

The total synthesis of ( )-ancistrofuran has relied on the ene reaction of N-phenyltriazolinedione (PTAD, 564) with the alkylidene lactone (563) (81JOC1198,80JOC4287), Upon completion of this room temperature reaction an attempt was made to acetylate the free NH group in (565) (2 1 mixture of diastereoisomers). The cyclized ethers (566) and (567) were, however, obtained instead. The triazolinedione thus functions as a very good... 

From a purely synthetic viewpoint, triazolinedione adducts have served as substrates for gaining access to numerous target molecules such as prismane, semibullvalene, bridged semibullvalenes, elassovalene, caged compounds, and azoalkanes. Indeed, the title reagent can be used not only as a chiral source, but also as an azo donor. In the synthesis of 4,5-diazatwis-4-ene, for example, (-)- nfirst step involved cycloaddition to cyclooctatetraene dibromide with formation of a separable mixture of diastereoisomers. Eventual removal of the... 

Applications of (-)-enasymmetric synthesis in cycloaddition reactions have shown low levels of induction. In the examples studied, (-)-endo-bomyltriazolinedione reacted almost instantaneously with various dienes even at low temperature (<96°C) resulting in low asymmetric induction (<10%). The high reactivity of triazolinedione in [4 + 2] tt-cycloadditions due to its high dienophilicity minimized differentiation between the transition states and has to date impeded its use in asymmetric synthesis. 

Reaction of a cyclopropane with diazomethane or an azide generated cyclopropanes containing an azo function " a similar cycloaddition was reported for a nitri-limine. Cycloaddition of an ethandiylidene biscyclopropane and triazolinedione led to a hydrazine derivative Reactions of these types forming azo- or hydrazinocyclopro-panes are not subject of this review however, they could be of interest for aminocyclop-ropane synthesis by functional group interconversion (for the cycloaddition of cyclopropyl azide with a carbon-carbon double bond see Section II.E.3, equation 101). 

The reaction of 1,-phenyl-1,2,4-triazolinedione occurs at the 1,4-position of the vinylcyclopropane system of benzvalene. This reaction has been used for the synthesis of prismane as mentioned before 39) (see Eq. 37). 

The use of azoalkanes as synthetic intermediates is illustrated in Schemes 17 and 18. We also note the general methodof formation of azoalkanes via intramolecular cyclization of unsaturated tosylhydrazones under acidic conditions (Scheme 19). The reaction of (103) gave products of intermolecular condensation. Structure (104) was established by X-ray analysis. Use of the optically active triazolinedione (105), derived from camphor, has enabled the synthesis of optically active 4,5-diazatwist-4-ene (106), and the absolute... 

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