Dialkylamino isocyanates

Dialkylamino isocyanates are known transient intermediates and, in the absence of other reagents, have been shown to dimerize. When the cyclic aminimide (c) was heated at 130°C under vacuum (0.3 mm) for 3 h, (d) was obtained in 89% yield. At higher temperature (d) was formed but rearranged to (e) as depicted in scheme 146. 

A, A -Dialkylamino isocyanates 153, generated from l,l-dimethyl-4-t-butyl-1,2,4-triazolidine-3,5-dione-l,2-aminimide 152, react with aliphatic isothiocyanates to give the [3+2] cycloadducts 154 resulting from addition across the C=N bond of the isothiocyanate... 

Kaugars and Rizzo have found that 5-alkylamino- or 5-arylamino-l,2,3,4-thiatriazoles react with isocyanates to give 3-oxo-A4-l,2,4-thiadiazolin-5-ylureas (65) (79JOC3840). The structures were verified by independent synthesis and by H and I3C NMR spectroscopy. In the presence of triethylamine the exothermic reaction went to completion in a few hours. The reaction may either take place by attack at the amino group to give (63), followed by N2 extrusion to form the reactive dipole (64 equation 31), or the reaction may be initiated by attack at the ring in the 4-position to give an intermediate thiatriazoline, which, as discussed above, reacts with heterocumulenes (see Section 4.28.2.3.l(iii)). As expected, 5-(dialkylamino)thiatriazoles were not found to react with isocyanates. 

Formamidines are accessible from 2-diaIkylamino-2-aIkoxyacetonitriles (360 Scheme 63) and primary amines. The action of HCN on the nitriles (360) gives rise to formation of A7-vinylamidines (361). ° Formamidines (362) are formed from bis(dialkylamino)acetonitriles and isocyanates in excellent yields. This reaction is interesting from the mechanistic point of view. 

Evidence has been advanced to show that 2-(A,A-dialkylamino)-l,3-oxazin-6-ones (8) exist in equilibrium with vinyl isocyanates (9), probably through the intermediacy of an iminoketene and a... 

The reaction of phosgene with l,l-dialkyl-2-arylazoguanidines (28) yields 6-dialkylamino-3-aryl-1,2,3,5-tetrazin-4-ones (29) (Equation (3)). These products decompose on heating at 120°C to give nitrogen, dialkylcyanamides, and aryl isocyanates. The tetrazinones decompose in the same way... 

The reaction of the difluoro compound CXXI with KOCN yields the isocyanate dimer CXXII and l,2-bis(dialkylamino)-l,2-diisocyanatoethylene (CXXIII) ( ). 

As the third component in the reaction of isocyanates with isonitriles enamines can also be used In this three-component reaction the isonitrile can be replaced by sulfur. Five-membered ring heterocycles are also formed from two equivalents of isocyanates and 2,2-bis(dialkylamino)-acetonitrile. This reaction proceeds via initial dissociation of the nitrile with formation of an isonitrile . 

The reaction of 2-(dialkylamino)-l,3-thiazol-4-amines with aryl isocyanates, led to the formation of thiazolopyrimidinediones 142 (Scheme 65) in good to high yields [99],... 

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