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Phosphinoboration of Diazobenzene: Intramolecular FLP Synthon for PN 2 B‐Derived Heterocycles
Author(s) -
LaFortune James H. W.,
Trofimova Alina,
Cummings Haley,
Westcott Stephen A.,
Stephan Douglas W.
Publication year - 2019
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/chem.201903670
Subject(s) - chemistry , frustrated lewis pair , synthon , adduct , stereochemistry , intramolecular force , acceptor , azide , reactivity (psychology) , medicinal chemistry , lewis acids and bases , boron , borane , catalysis , organic chemistry , medicine , physics , alternative medicine , pathology , condensed matter physics
Phosphinoboration of diazobenzene with Ph 2 PBR′ 2 cleanly affords products of the form Ph 2 P(PhNNPh)BR′ 2 ( 2 : R′ 2 =catechol, cat; 4 : R′ 2 =phenanthrenediol, quin) and shows evidence of Ph 2 P(PhNNPh)Bpin 7 (pin: pinacol). The mechanism of these reactions was probed computationally and shown to proceed via intermediates involving a diazobenzene‐adduct of the boron center of the PB reagent. The resulting PNNB species 2 and 4 are shown to be frustrated Lewis pairs (FLPs). Despite the presence of weakly Lewis acidic boron centers, these species react with diazobenzene. Additionally, the FLP reactivity of 2 was further probed with 4‐phenyl‐1,2,4‐triazole‐3,5‐dione, 1,10‐phenanthroline‐5,6‐dione, and benzyl azide to give unique five‐, six‐, and eight‐membered heterocyclic rings. Thus, phosphinoboration provides a new avenue to FLPs in which donor and acceptor sites are linked by nitrogen atoms.