Azidocinnamates

The cinnamate ester prepared as above (23.2 g. 79 mmol) was added as a solid slowly to refluxing xylene (500 ml) over a period of 3 h at a rate that prevented accumulation of unreacted azidocinnamate in the solution (monitored by gas evolution through a gas bubbler). The solution was refluxed for an additional 2 h after gas evolution ceased. The reaction mixture was cooled and the solvent removed in vacuo. The residue was recrystallized from methanol to give pure product (20.7 g, 99% yield). 

To a solution of 1.84 g Na metal in 60 ml ethanol at 5-10° add, over Vi hour with vigorous stirring a mixture of 0.08 M ethyl azidoacetate and 0.02 M 2 (or 2,5 2,3 etc. but not 6) substituted benzaldehyde and continue stirring at 5-10° until nitrogen evolution ceases (about V2-I hour) then stop immediately and rapidly evaporate in vacuum Vi the ethanol (keep temperature below 30°). Basify the solution with solid NH CI, dilute with 500 ml water and extract 3 times with ether. Filter, wash with water to neutrality and dry, evaporate in vacuum the ether (or can dissolve the residue in petroleum ether, or 1 1 petroleum ether.benzene for methoxy compounds, and filter through silica gel) to get the ethyl-alpha-azidocinnamates (1) in about 50% yield. Store in freezer until used in next step. Dissolve 1 g (I) in 100 ml p-xylol and reflux 10 minutes. Evaporate in vacuum (or add 5 ml pentane, filter, evaporate in vacuum) to get about 90% yield of the 4 substituted-2-car-bethoxyindole which can be decarboxylated as described elsewhere here. 

Quinazolines have become increasingly important as biologically active principles, e.g., as antiseptics or antimalarials. An interesting approach to this class consists of a combination of the aza-Wittig reaction with photochemical processes, as shown in Scheme 76. o-Azidocinnamates (206) are cyclized with the aid of triethyl phosphite to afford 2-alkoxyquinolines... 

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). 

Iminophosphoranes derived from readily available ot-azidocinnamates react with aroyl chlorides to give the corresponding 2-aryl-4-arylidene-5(4//)-oxazolones 37 2 500,501 AjteiTjatively, these iminophosphoranes are converted to the corresponding 2-arylamino-4-arylidene-5(4//)-oxazolones 373 via heterocyclization of an intermediate carbodiimide as shown in Scheme 7.119 (Table 7.32, Fig. 7.43). ° ... 

Nitrenes insertion is effective for the synthesis of azepines by thermolysis of o-styryl azidocinnamates (86JCS(P1)1113). Thus, the vinylazidocinnamate (209) yields the 3-benzazepine (210) (90JCS(P1)2929). 

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] ... 

This reaction has been employed for the synthesis of saturated and unsaturated amino acids by cathodic reduction of azidocinnamic esters [237]. Reduction of azides in DMF in the presence of acetic anhydride yields diacetylated amines [237]. Azide groups in activated methylene groups may, however, be reduced to azide ion and methyl compound [236]. 

Photocross I inking of poly(vinyl-p-azidocinnamate) (XIII) is reported to involve competitive photodimerization of cinnamoyl groups to cyclobutenes along with the dominant nitrene reactions of insertion and radical abstraction. The reaction can be triplet-sensitized (19). 

Abstract Although aromatic azides are believed not to emit phosphorescence, 2,4,6-tribromophenylazide was found to phosphoresce in EPA at 77°K, and the peak of the spectrum coincides with the tail of the absorption spectrum of its concentrated solution in ethyl iodide. The measurements of the So-)Ti absorption spectra in ethyl iodide with vibrational structures were also succeeded in the cases of ethyl p-azi-dobenzoate and ethyl azidocinnamate. The experimantal values coincided with the )3 transition energies estimated by SCF MO Cl... 

Triplet States. The measurement of the Sq- T-i transition energy was succeeded in the case of ethyl p-azidocinnamate, too(Fig.5(b)). 

Figure 7. Comparison of the calculated values with the experimental ones on the electronic transition energies and oscillator strengths of the p-azidocinnamate (ethyl p-azidocinnamate in n-hexane)...

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... 

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