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Abstract:
The title compound is synthesized starting from either 4‐bromobenzyl tert‐butyldimethylsilyyl ether (5b) or 4‐bromobenzyl tert‐butyl ether (5c) or – most simply – from 4‐bromotoluene (5a). In the first step Br was replaced by Li using n‐butyllithium, then the organometallic compounds were converted into the respective trifluoroacetophenones 6a–c with N‐trifluoroacetylpiperidine. The azi moiety (diazirine) was prepared from the oximes 7a–c viaO‐tosyloximes 8a–c plus ammonia yielding the diaziridines 9a–c and oxidation of the latter with Ag2O. Oxidation by permanganate – of the ethers after acidic cleavage – yields the title compound 12. On irradiation (λ > 300 nm) 12 by elimination of N2 with a half‐life period of 22 s generates the corresponding carbene. At the same time from 12 with ca. 20% the yellow isomeric 4‐(1‐diazo‐2,2,2‐trifluoroethyl)benzoic acid (20) is formed which is photolyzed generating the same carbene as 12. The synthesis of 20 is described starting from 4‐bromobenzaldehyde. – The diazirine 12 as its N‐hydroxysuccinimide ester 13, or using other methods of amide synthesis, can readily be coupled to amino functions of biochemically interesting agents thus forming photoaffinity labels.
