2//-Azirine, 3-dimethylamino-2,2-dimethyl

Recent examples of this synthesis are of two types. The first involves condensation of the activated phenol, 2-amino-4,6-dinitrophenol (346a) with 2-dimethyl-amino-3,3-dimethyl-3//-azirine (346b) (in MeCN, 0°C- 20°C, A, 24 h) to afford a separable mixture of four products, one of which was 2-dimethylamino-3,3-dimethyl-5,7-dinitro-3,4-dihydroquinoxaline (346c) ( 20% yield) and another its hydrolysis product, 3,3-dimethyl-5,7-dinitro-3,4-dihydro-2(l//)-quinoxalinone (346d) ( 8%) the mechanism of such condensations has been discussed. ... 

The reaction of 4-methyl-2,3,4,6-tetrahydro[l,2,4]triazino[3,4-a]-isoindole-3,6-dione 671 with 3-dimethylamino-2,2-dimethyl-2//-azirine... 

Heimgartner and co-workers conducted a detailed mechanistic investigation of the reaction of [ NJlabeled 2,2-dimethyl-3-(dimethylamino)-27/-azirine 332 with NH-acidic heterocycles (Scheme 6.71). Based on these studies the authors proved that ring opening of 188a with 332 afforded the imidazolone 336 in which... 

It was also reported " that the reaction of 4,4-disubstituted-2-(trifluoromethyl)-5(4f/)-oxazolones 251 with 2,2-dimethyl-3-(dimethylamino)-2//-azirine afforded 5-(dimethylamino)-3,6-dihydropyrazin-2(l//)-ones 252 (Scheme 7.81). In this case, the reaction only occurs when electron-withdrawing substituents are present at C-2 of the oxazolone. 

The reaction of a-amino ketones (508d) with thiosemicarbazides (761) affords 3-amino-4,5-dihydro-l,2,4-triazines (762) and the dihydrotriazine-3-thiones (763) (57MI21900). 2,2-Dimethyl-3-dimethylamino-2i/-azirine (764) reacts with benzohydrazides (765 R = Ar) via the open-chain intermediates (766) to give 3-aryl-6-dimethyIamino-2,5-dihydro-l,2,4-triazines (767 R = Ar). With ethyl carbazidate (765 R = OEt) the corresponding triazin-3-one (768) is formed (78HCA2419,78C332). 

Dimethylamino-2,2-dimethyl-2//-azirine (23) and methyl 2-amino-3-phenyl-propionate gave 3-benzyl-5-dimethylamino-6,6-dimethyl-3,6-dihydro-2(17/)-... 

Dimethylamino-2,2-dimethyl-2//-azirine (27) and 4-isopropyl-2-trifluo-romethyl-5-oxazolinone (28) gave 5-dimethylamino-3-isopropyl-6,6-di-methyl-3,6-dihydro-2(l//)-pyrazinone (29) (MeCN, reflux, N2, 1 h 60% a rational mechanism was suggested) 944 analogues, like 3-allyl-5-dimethy-lamino-6,6-dimethyl-3-phcnyl-3,6-dihydro-2(l//)-pyrazinone (44%),958 were made similarly.944 958... 

Dimethyl-3-dimethylamino-2//-azirine (X) was reacted (a) with BFs-etherate at -78°C in CH2CI2, (b) with benzamide (Y) in the presence of sodium hexamethyldisilazane in THF at -78°C. After workup, a new heterocylic product (A) was isolated in 49% 5neld (together with 49% of unreacted Y). 

The reaction of 2 with 3-(dimethylamino)-2,2-dimethyl-2//-azirine (83) affords in 94% yield the diamide (R)-( — )-2-(2-hydroxy-2-phenylacetamido)-A, A -2-trimethylpropionamide (84). Selective acidic hydrolysis of 84 with gaseous hydrogen chloride in acetonitrile-water provides the acid 85. The hydroxyl group is protected as a THP ether and the compound is converted to the depsipeptide 86 in good yield. Cyclization of 86 occurs with gaseous hydrogen chloride in toluene at 100 °C to furnish in 88% yield cyclo[(7 )-Mns-Aib-(7 )-... 

H,3 0-Phthalazinedione (89) with 2-dimethylamino-3,3-diniethyl-3//-azirine (90) gave 3-dimethyliminio-2,2-dimethyl-2,3-dihydroimidazo[2,l-n] phthalazin-6-olate (91) (substrate, Me2NCHO, 60°C 20°C, 30 min syn-thon in Me2NCHO dropwise 20°C, 18 h 84%). ... 

Dimethylamino-3,3-dimethyl-2-azirine evaporated slowly through a glass tube filled with glass beads and heated at 340°/0.1 mm l-dimethylamino-3-methyl-2-azabutadiene. Y 97% purity 95%. F. e. and conversion of the products into pyridine rings s. A. Demoulin et al.. Am. Soc. 97, 4409 (1975). 

An ethereal soln. of trimethylsilyl isocyanate added with stirring to a soln. of startg. azirine in ether, then after a few min methanol in ether added slowly - 4-(dimethylamino)-5,5-dimethyl-3-imidazolin-2-one. Y 78%. F.e., also 4-amino-A -2-imidazolinethiones with trimethylsilyl isothiocyanate, s. I. Handke, E. Schaumann, J. Org. Chem. 53, 5298-300 (1988). 

Bromocycloheptanone is reduced to cycloheptanone by titanocene dichloride and magnesium. Vinyl acetates, including 1- and 2-acetoxycyclohepta-1,3-dienes, have been prepared from vinyl bromides using copper(i) acetate. a-Formylcyclo-heptanone reacts with 2,2-dimethyl-3-dimethylamino-2ff-azirine to give adduct (320). Electrochemical reduction of some seven-membered cyclic P-diketones has been studied polarographically/ ... 

Type B (C—C—N + C—S) Syntheses.—Benzoyl isothiocyanate reacts with 2,2-dimethyl-3-dimethylamino-2/f-azirine to give the interesting dipolar compound 4,4-dimethyl-A -thiazoline-5-dimethylimminium-2-benzocarboxamidate... 

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