Photochemical transformations of small-ring heterocyclic compounds. 99. 1,4-Substituent shifts in the photorearrangement of 2-hydroxymethyl-2H-azirine derivatives to N-Vinylimines

Padwa, Albert; Carlsen, Per H. J.; Tremper, Alan

doi:10.1021/ja00482a028

Cited by 23 publications

(4 citation statements)

References 26 publications

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“…Path a has been observed previously by Wendling and Bergmann, − but path b (formation of ketenimine ( 23 )) has not. The conditions used by these authors were not FVT; instead, the reactions were carried out at atmospheric pressure using helium as a carrier gas and residence times of ca.…”

Section: Resultssupporting

confidence: 50%

Nitrile Imines and Nitrile Ylides: Rearrangements of BenzonitrileN-Methylimine and Benzonitrile Dimethylmethylide to Azabutadienes, Carbodiimides, and Ketenimines. Chemical Activation in Thermolysis of Azirenes, Tetrazoles, Oxazolones, Isoxazolones, and Oxadiazolones

et al. 2014

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Flash vacuum thermolysis (FVT) of 1-methyl-5-phenyltetrazole (5b), 2-methyl-5-phenyltetrazole (1b), and 3-methyl-5-phenyl-1,3,4-oxadiazol-2(3H)-one (3b) affords the nitrile imine (2b), which rearranges in part to N-methyl-N'-phenylcarbodiimide (7b). Another part of 2b undergoes a 1,4-H shift to the diazabutadiene (13). 13 undergoes two chemically activated decompositions, to benzonitrile and CH2═NH and to styrene and N2. FVT of 2,2-dimethyl-4-phenyl-oxazol-5(2H)-one (16) at 400 °C yields 3-methyl-1-phenyl-2-azabutadiene (18) in high yield. In contrast, FVT of 3,3-dimethyl-2-phenyl-1-azirene (21) at 600 °C or 4,4-dimethyl-3-phenyl-isoxazolone (20) at 600 °C affords only a low yield of azabutadiene (18) due to chemically activated decomposition of 18 to styrene and acetonitrile. There are two reaction paths from azirene (21): one (path a) leading to nitrile ylide (17) and the major products styrene and acetonitrile and the other (path b) leading to the vinylnitrene (22) and ketenimine (23). The nitrile ylide PhC(-)═N(+)═C(CH3)2 (17) is implicated as the immediate precursor of azabutadiene (18). FVT of either 3-phenylisoxazol-5(4H)one (25) or 2-phenylazirene (26) at 600 °C affords N-phenylketenimine (28). The nitrile ylide PhC(-)═N(+)═CH2 (30) is postulated as a reversibly formed intermediate. N-Phenylketenimine (28) undergoes chemically activated free radical rearrangement to benzyl cyanide. The mechanistic interpretations are supported by calculations of the energies of key intermediates and transition states.

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Section: Resultssupporting

confidence: 50%

Nitrile Imines and Nitrile Ylides: Rearrangements of BenzonitrileN-Methylimine and Benzonitrile Dimethylmethylide to Azabutadienes, Carbodiimides, and Ketenimines. Chemical Activation in Thermolysis of Azirenes, Tetrazoles, Oxazolones, Isoxazolones, and Oxadiazolones

et al. 2014

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“…Therefore, a series of efficient and simple methods for synthesizing polysubstituted oxazoles have been developed . Despite these applications, few methods for the introduction of a trifluoromethyl (−CF 3 ) group onto oxazole rings, which may change the metabolic stability, lipophilicity, and biological properties of oxazole compounds, have been reported. In this regard, the development of efficient methods for preparing trifluoromethyl-decorated oxazoles has long been a hot and challenging topic in molecular synthesis.…”

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Copper-Catalyzed Three-Component Domino Cyclization for the Synthesis of 4-Aryl-5-(arythio)-2-(trifluoromethyl)oxazoles

et al. 2019

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“…The hydroxy group in 2-(hydroxymethyl)-2H-azirines can be converted into a chloride by means of carbon tetrachloride and hexamethylphosphoric triamide or into the bromide via the intermediate mesylate. [460] By reaction with benzoyl chlorides in pyridine at room temperature, the corresponding esters can be obtained in 63-81% yield. Boron trichloride catalyzed Prins-type reaction of alkenes R 1 CH=CH 2 [R 1 = Bu, (CH 2 ) 5 Me, iBu, s-Bu, t-Bu, Bn] with trichloroacetonitrile gives rise to 2,2-dichloro-3-(2-chloroalkyl)-2H-azirines in high yields, which can be converted into 3-alkenyl-2,2-dichloro-2H-azirines by a triethylamine-promoted elimination of chloride.…”

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confidence: 99%

“…[463] The 2-formyl group may also be alkenated using Wittig reagents such as [(ethoxycarbonyl)methylene]triphenylphosphorane. [460] Azirines also undergo alkylation and silylation reactions. Thus, if 2,3-dimethyl-2-phenyl-2H-azirine is treated with butyllithium, followed by reaction with iodomethane, allyl iodide, or benzaldehyde, alkylation in the AE-position of the imine occurs.…”

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confidence: 99%

Product Class 7: Imines

Padwa¹,

Bellus²

2005

Category 4. Compounds With Two Carbon Heteroatom Bonds

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Compounds with the general structure R 1 R 2 C=NR 3 , referred to as imines, were first obtained by Schiff via condensation of ketones and aldehydes with primary amines. Therefore, the condensation products are also called Schiff bases. In addition, the nominations azomethine, ketimine (derived from ketones), aldimine (derived from aldehydes), and anil (derived from anilines) are in use. It is recommended that the terms imine(s), ketimine(s), or aldimine(s) are used, rather than Schiff base(s) or azomethine(s).Since imines have to be considered as analogues of carbonyl compounds, many of the chemical properties are similar to the latter. Imines are used in new C-C bond formations, and reactions with electrophiles (e.g., aldehydes, alkyl halides), and the C=N moiety can undergo nucleophilic reactions. Generally, imines are very useful compounds in organic synthesis, as they are used in several syntheses of aza-heterocyclic compounds. Most imines are stable in an alkaline medium and therefore can be dried over potassium hydroxide. In diluted acid, however, they are easily hydrolyzed. In many cases intermediary imines cannot be isolated because of their lability. The presence of a C=N bond creates the possibility for E/Z isomerism (syn/anti). It has been recognized that such geomet-

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Photochemical transformations of small-ring heterocyclic compounds. 99. 1,4-Substituent shifts in the photorearrangement of 2-hydroxymethyl-2H-azirine derivatives to N-Vinylimines

Cited by 23 publications

References 26 publications

Nitrile Imines and Nitrile Ylides: Rearrangements of BenzonitrileN-Methylimine and Benzonitrile Dimethylmethylide to Azabutadienes, Carbodiimides, and Ketenimines. Chemical Activation in Thermolysis of Azirenes, Tetrazoles, Oxazolones, Isoxazolones, and Oxadiazolones

Nitrile Imines and Nitrile Ylides: Rearrangements of BenzonitrileN-Methylimine and Benzonitrile Dimethylmethylide to Azabutadienes, Carbodiimides, and Ketenimines. Chemical Activation in Thermolysis of Azirenes, Tetrazoles, Oxazolones, Isoxazolones, and Oxadiazolones

Copper-Catalyzed Three-Component Domino Cyclization for the Synthesis of 4-Aryl-5-(arythio)-2-(trifluoromethyl)oxazoles

Product Class 7: Imines

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