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Photochemical Isomerizations of 5‐Alkylidene‐4,5‐dihydro‐3 H ‐1,2,4( λ 3 )‐diazaphospholes (4‐Phosphapyrazolines): (5→4) Ring Contraction Generates Azomethineimine Dipoles
Author(s) -
Manz Berthold,
Kerth Jochen,
Maas Gerhard
Publication year - 1998
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/(sici)1521-3765(19980515)4:5<903::aid-chem903>3.0.co;2-j
Subject(s) - chemistry , irradiation , cycloaddition , photochemistry , dipole , photodissociation , contraction (grammar) , spectroscopy , stereochemistry , organic chemistry , catalysis , physics , biology , quantum mechanics , nuclear physics , endocrinology
A skeletal rearrangement rather than the expected elimination of molecular nitrogen is the result of UV irradiation of 4‐phosphapyrazolines 1 [Eq. (1)]. If R 1 is an alkyl group, the resulting azomethineimine dipoles 2 can be detected by spectroscopy and trapped in a 1,3‐dipolar cycloaddition reaction; on prolonged irradiation, they undergo further skeletal rearrangement. A phosphindole is obtained after irradiation of 1 (R 1 = 4‐anisyl).