Triazolinediones, addition

An important type of N- alkylation involves the addition of cyclic or acyclic C=CH to reactive triazolinediones (76 Scheme 27) (8ihc(37)1, p. S3o). However (76) may behave as the 7T-system to which piperidine adds to yield (81) ( 6jhc673) or again it acts as a powerful dienophile affording (82) in Scheme 27 (75jcs(P2)i325). 

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... 

That this difference in (4+2)-cycloaddition behavior most likely has steric origins—the methyl groups in 150 or the derived monoadduct preventing an ortho -addition of two equivalents of the dienophile—is supported by the observation that permethyl[6]radialene 95 is inert even towards the extremely reactive dienophile 4-phenyl-1,2,4-triazolinedione. ... 

Paquette s group has recently synthesized and evaluated chiral 4-sub-stituted triazolinediones in Diels-Alder cycloadditions.63 For example, endo-(-)-bomylamine has been converted to an azo dienophile, which has been used to resolve 1,2,3-trimethylcyclooctatetraene (Scheme 6-VII). In addition, triazolinediones derived from a-methylbenzylamine and dehydroabietylamine have been prepared and their reactions with achiral 1,3-dienes were investigated.636 Unfortunately, these dienophiles did not show good kinetic enantioselection, but they are useful for the type of resolution shown in Scheme 6-VII.630... 

A detailed classification of two-electron cyclo-addends includes A(-phenyl-triazolinedione (PTAD). Enantiomerically pure unsaturated [4.4.2]pro-pellanes have been isolated by means of Diels-Alder addition of (—)-endo-bornyltriazolinedione followed by separation of the resulting diastereoisomeric urazoles and re-formation of the propellanes. The product (39) of 1,7-dipolar cyclization of a conjugated carbonyl ylide has been intercepted by addition of PTAD across the diene moiety, as has the dimer of cyclo-octa-... 

Dimethyl-1-phenylphosphole selenide gave adducts with maleic anhydride (49%) and N-phenylmaleimide (72% <85PS(25)20l . With the triazolinediones, the addition products fragmented easily. 

It has also been known for many years that the ene reaction with compounds such as 4-substituted-l,2,4-triazoline-3,S-diones can be applied to dienic polymers, either to achieve chemical modification, or, with difiinctional compounds, crosslinking. Butler et alP have now undertaken a detailed study of the addition of triazolinediones (R = CH3, C H5) to a range of diene polymers and copolymers. 

The alkenylidenecyclopropanes (104) and (105) react thermally with the electron-deficient acetylenes (106) exclusively in a [2 + 2] fashion to yield a mixture of the methylenecyclobutenes (107) and (108)." The preference for [2 -I- 2] addition in this reaction is in marked contrast to the course of the reaction between alkylidenecyclo-propanes and either 4-phenyl-1,2,4-triazolinedione or chlorosulphonyl isocyanate, neither of which gives any [2 -I- 2] addition products. 

Strained polycyclic azo-compounds offer a variety of uses to the organic chemist, and several attractive syntheses have been described (cf. Vol. 3, p. 177 Vol. 4, p. 186 Vol, 5, p. 199). One such method is the oxidative hydrolysis of urazoles for which a new convenient and mild method has now been described. In all cases the new hydrazinolysis method (Scheme 41) gave yields at least as good as or better than previous methods. Addition of triazolinedione to bi-cylobutane, followed by oxidative hydrolysis gives the previously unprepared azo-compound (31), which decomposes to give bicyclobutane. ... 

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