A-Azidocinnamates

Kurita et al. reacted a-azidocinnamate 327 with benzoyl chloride (Scheme 119) to form benzoate 328, which upon conversion of the azide group into an iminophosphorane (329) underwent an aza-Wittig cyclization to yield 1,3-benzoxazepine (330) (92CC81). 

In analogy to the benzoxazepines, Kurita et al. have also synthesized 1,3-benzodiazepines (91TL4401) from o-acylamino-a-azidocinnamates (92CC81). 

The base-catalyzed condensation of a-azido esters and ketones with aromatic aldehydes has recently been developed as a new vinyl azide synthesis.42,43 The yields range from moderate to excellent in some cases. The thermal decomposition of ethyl a-azidocinnamate (87) in xylene gives only 2-ethoxycarbonylindole (88).44 The unstable 2-ethoxycarbonyl-3-phenyl-l-azirine could be detected if the thermolysis was carried out at a lower temperature. This fact indicates that the 1-azirine is probably an intermediate leading to the indole, although the intermediacy of the vinyl nitrene could not be established. This result is similar to that observed by Isomura et al. on the pyrolysis of terminal vinyl azides.27,28... 

In aprotic media, a-azidostyrenes have been reduced in the presence of acetic anhydride to mono- and diacetylated enamines and further reduced compounds [225]. a-Azidocinnamic esters may under similar conditions be reduced to A,A-diacetylated a-aminocinnamic ester or, by careful addition of a proton donor, to o -aminocinnamic ester [226] ... 

It is reported by Meth-Cohn et al. that, in contrast to earlier claims, the ketone-sensitised reaction of a-azidocinnamates gives a high yield of the intermediate pair of aziridinoimidazoline dimers, and Hoffmann et al. have used the irradiation of aziridines such as 39 to access novel compounds of type... 

Z)-a-Azidocinnamic esters cycUze to afford 2-indolecarboxylic esters on thermolysis ( 145°). The reaction temperature is lowered to 30°-60° by catalysis of Rh2(OCOC3F7)4 [but not by Rh2(OAc)4]. Similarly, 2-aryUndoles are synthesized from o-azidostilhenes by warming with Rh2(OCOC3Fv)4 and 4A-molecular sieves in toluene at 60°. ... 

Using Ph3P to induce Staudinger reaction of a-azidocinnamic esters as well as Wolff rearrangement of a-diazo ketones, two types of mutually reactive molecules are formed. The natural course for aza-Wittig reaction is pursued to produce cyclization-prone ketene imines. ... 

Hemetsberger and coworkers published in 1969 the special condensation reaction of benzaldehydes 76 with ethyl azidoacetate (77a) in the presence of sodium ethoxide to get moderate to good yields of the a-azidocinnamic esters 79a (Scheme 5.12). The temperature and the reaction time had to be controlled careMly, because the strongly alkaline reaction conditions induced the danger of decomposition of the base-sensitive azides 77 and other unwanted side reactions. Thus, Knittel reported some years later that usage of methyl azidoacetate (77b) and sodium methoxide offers several advantages in the synthesis of vinyl azides 79b. Nevertheless, the Hemetsberger-Knittel reaction can only be... 

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