Triazolinedione reactions

Chen, J., Houk, K. N., Foote, C. S., 1998, Theoretical Study of the Concerted and Stepwise Mechanisms of Triazolinedione Diels-Alder Reactions , J. Am. Chem. Soc., 120, 12303. 

This investigation was undertaken to study the important variables in the hydrophilization of polydiene surfaces by ene reaction with triazolinediones (Step 1) followed by neutralization (Step 2) as shown below. These variables included the nature of the... 

The low temperature ene reaction of triazolinediones with polydienes occur under heterogeneous conditions to yield hydrophilic surfaces, especially after neutralization of the resulting pendant urazole groups. Permanent hydrophilic surfaces can be obtained when (TD)2DPM is used. The use of the other RTDs tested results in surfaces that lose their hydrophilicity within 5-20 days. In applications such as improving the adhesion of rubber to other substrates, these reagents are probably sufficient (18). However, when more permanent hydrophilic surfaces are desired a bis-triazolinedione such as (TD)2DPM would be required. 

Formate esters behave as typical carbonyl compounds in reactions with a number of ylides, eliminating phosphine oxide and forming vinyl ethers, e.g. (33).35 Stabilized phosphoranes are able to condense with the carbonyl group of cyclic thioanhydrides (34).38 Quinoline derivatives, e.g. (35), are obtained from the condensation of dicar-boalkoxy-ylides with isocyanates.37 Benzoyl isothiocyanates and keto-phosphoranes give quantitative yields of (36), which are unreactive in Wittig reactions but can be readily oxidized by selenous acid.38 The products obtained from reactions (Scheme 9) with the triazolinedione (37) depend upon the stability of the ylide used.39... 

Density functional theory has been used to investigate the Diels-Alder reactions of triazolinedione with s-cis- and. y-fran -butadiene. " Combined quantum mechanics-molecular mechanics calculations have been used to investigate the asymmetric Diels-Alder reaction of cyclopentadiene with the complex dienophiles AICI3-methyl acrylate and methoxyaluminium dichloride-acrolein.Equilibrium constants have been determined for the molecular complexes formed from 1-alkyl-1-(2-naphthyl)ethenes and 1-vinylnaphthalene with TCNE in C1(CH2)2C1 at 27.1 °C ... 

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... 

A reaction mechanism in which the / carbon of the vinyl azide attacks the N-N double bond of the triazolinedione to give an intermediate which cyclizes with loss of nitrogen to the triazoline has been proposed (Scheme 3).6... 

Consideration of the energetics of the sequence suggested that an intermediate like 31 might accumulate to observable concentrations in reactions of the triazolinedione with reactive alkenes whose structural features disfavour the [1,5]-hydrogen shift and, indeed,... 

Simple 2/7-chromenes produce [2+2] cycloaddition products upon reaction with triazolinediones such as phenyl-triazolinedione (PTAD) and methyl triazolinedione (MTAD) (Equation 11) <1995T13277>. 

Another series of publications from Ken s group compared kinetic isotope effects, computed for different possible transition structures for a variety of reactions, with the experimental values, either obtained from the literature or measured by Singleton s group at Texas A M. These comparisons established the most important features of the transition states for several classic organic reactions — Diels-Alder cycloadditions, Cope and Claisen rearrangements, peracid epoxidations, carbene and triazolinedione cycloadditions and, most recently, osmium tetroxide bis-hydroxylations. Due to Ken s research, the three-dimensional structures of many transition states have become nearly as well-understood as the structures of stable molecules. 

Both cyclic and acyclic R-N = N — R systems undergo ene reactions with simple alkenes, and most studies have employed either A -substituted triazolinediones 1 or azodicarboxylate diesters 3 to produce the triazolidines 2 and the hydrazines 4, respectively. 

This reaction picture is somewhat clouded by a recent report detailing the stereochemical outcome of the reactions of the alkenes 6 and 7 with diethyl azodicarboxylate and N-phenyl-triazolinedione to produce the two sets of diastereomers 8, 9 and 10, IT, respectively10. 

Exceptions to the generalization of poor regiocontrol with triazolinediones involve ene partners where one mode of reaction would place the nitrogen in the adduct adjacent to a tertiary or quaternary center, shown in the formation of 1212-13. 

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. 

Since their introducticm by Cookson et al. in 1962, 4-substituted l,2,4-triazoline-3,5-diones have been used extensively as dienophiles (equation 62). These dienophiles are highly reactive towards most 1,3-dienes and undergo cycloadditions under very mild conditions. In general, these Diels-Alder reactions are syn selective with respect to the diene, although with some (Z)-dienes this selectivity is lost. As noted above, it has been found that these cycloadditions are stepwise reactions in (Z)-dienes which cannot achieve an s-cis conformation. However, it is not clear if tdl cycloadditions of triazolinediones with 1,3-dienes proceed this way. 

Single electron donors such as sodium metal, sodium iodide, or sodium naph-thalenide (the last in an amount as low as 5 % molar) convert triazolinediones to deaza dimers 77 via a reaction that has been formulated as a radieal anion chain... 

It should be pointed out, however, that in other cases an electrophilic reaction cannot be totally excluded. By virtue of the substituent effect, such a mechanism was invoked for the reactions of the highly electrophilic triazolinedione with bicyclobutane derivatives (equation 68) ... 

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