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Cycloadditions of 1H ‐1,3‐Benzazaphospholes with o ‐Chloranil
Author(s) -
Heinicke Joachim W.,
Gupta Nidhi,
Mayer Peter,
Karaghiosoff Konstantin
Publication year - 2020
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.202000067
Subject(s) - cycloaddition , chloranil , phosphinidene , chemistry , carbene , molar ratio , yield (engineering) , medicinal chemistry , organic chemistry , materials science , catalysis , metallurgy
NH‐Functional 1H ‐1,3‐benzazaphospholes 1a–1c and o ‐chloranil (tetrachloro‐ o ‐benzoquinone ‐ TCBQ) undergo rapid [1+4]‐cycloaddition in a 1:2 molar ratio to give 2a – 2c as high‐melting zwitterionic σ 6 λ 5 ‐phosphorus compounds. In the case of 2a the yield is high (rel. to TCBQ) even if the reactants were used in a 1:0.5 molar ratio. For the 2‐ tert ‐butyl‐substituted compounds 2b and 2c the yields were significantly lower, in part by unidentified byproducts. Addition of excess TCBQ to crude 2c containing unconverted 1c did not increase but strongly decrease the amount of 2c . Crystallization and XRD analysis led to detection of a minor side or consecutive product 3c , formally corresponding to P=C bond cleavage and [1+4] cycloaddition of three equivalents TCBQ, two at the phosphinidene and one at the carbene end. NMR spectroscopic data of 2a – 2c including conclusive 13 C data for 2a give evidence of the structures of the new compounds.