Photoinduzierte Reaktionen von 3‐Phenyl‐2<i>H</i>‐azirinen mit Carbonsäureestern 40. Mitteilung über Photoreaktionen

Gilgen, Paul; Hansen, Hans‐Jürǵen; Heimgartner, Heinz; Sieber, Willi; Uebelhart, Peter; Schmid, Hans; Schönholzer, Peter; Oberhänsli, Willi E.

doi:10.1002/hlca.19750580628

Cited by 27 publications

(1 citation statement)

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“…C 46,41 H 6,39 N 7,73% Gef. C 46,22 H 6,38 N 7,82% 1.2.3 : 175(Mt,14), 174 (19), 160 (lo),144 (12),134 (39,91 (Il),58 (25),43 (100). CIIHBNO (175,23) Ber.…”

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confidence: 98%

Zur Regioselektivität von Cycloadditionen photochemisch erzeugter Benzonitril‐isopropylide. 51. Mitteilung über Photoreaktionen

Gerber

Heimgartner

Schmid

et al. 1977

Helvetica Chimica Acta

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Socikte suisse de chimie, Bale -Societa svizzera di chimica, Basilea Nachdruck verboten -Tous droits rCserv6s -Printed by Birkhauser AG., Basel On the regioselectivity of cycloaddition reactions of photochemically generated benzonitrile-isopropylides SummaryThis paper deals with the physical and chemical differences of zwitterionic benzonitrile-isopropylides, which differ by a p-substituent in the phenyl ring (H, F, OCH3;Scheme 2). These dipolar species (4-6) are produced by irradiation of the corresponding 2H-azirines (1-3; Scheme I ) in a 2-methylpentane glass at -185". Their UV. spectra are reproduced in the Figure. The spectra of 4 and 5 are characterized by an 'aromatic band' at short wavelength, and a longer wavelength band at approximately 275 nm, which is considered to be characteristic of the nitrile-ylide system. The UV. spectrum of the methoxy derivative 6, which shows a broad absorption at 260 nm, arises by an addition of the 'nitrile-ylide band' and the anisole band. The three dipolar species 4-6 do not show any significant differences in the regioselectivity of the cycloaddition with methyl a-methacrylate even though F and OCH3 have quite different 6-constants (Scheme I ) . The addition according to modus A is very much preferred (B/A = 0,076). -It seems, that the substituents F and OCH3 do not affect the physical and chemical behaviour of the parent benzonitrile-isopropyiide (4). All three dipolar species 4-6 react regjospecifically according to modus A with methyl trifluoroacetate (Scheme 3). The regioselectivity is reduced in the cycloaddition of 4 with methyl propiolate and ethyl phenylpropiolate (B/A = 0,04 and 0,28, respectively). The reduced regioselectivity in the latter case may be attributed to a reduced polarity of the triple bond in the dipolarophile.

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“…C 46,41 H 6,39 N 7,73% Gef. C 46,22 H 6,38 N 7,82% 1.2.3 : 175(Mt,14), 174 (19), 160 (lo),144 (12),134 (39,91 (Il),58 (25),43 (100). CIIHBNO (175,23) Ber.…”

mentioning

confidence: 98%