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From BN‐Naphthalenes to Benzoborole Dianions
Author(s) -
Zhu Dezhao,
Guo Lulu,
Li Jianfeng,
Cui Chunming
Publication year - 2021
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.202101178
Subject(s) - dilithium , chemistry , salt (chemistry) , lithium (medication) , naphthalene , protonation , medicinal chemistry , yield (engineering) , inorganic chemistry , ring (chemistry) , organic chemistry , materials science , deprotonation , medicine , ion , metallurgy , endocrinology
Abstract The synthesis of benzoborole dianions by alkali metal reduction of BN‐naphthalene derivatives via a ring‐contraction strategy has been developed. Reduction of 1‐alkynyl 2,1‐benzazaborine 1 a in Et 2 O led to the elimination of alkynyllithium with the formation of 1‐amino‐1‐benzoborole trilithium salt 2 a , whereas reduction of 1‐phenyl 2,1‐benzazaborine 1 c in THF yielded 1‐phenyl‐1‐benzoborole dilithium salt 2 c with the elimination of ArNHLi. The trilithium and dilithium salts 2 a and 2 c have been fully characterized. Treatment of trilithium salt 2 a with Et 3 NHCl led to the selective protonation of the amino lithium to afford the dilithium salt 2 aH , which could be cleanly oxidized to 1‐amino‐1‐benzoborole 3 in an excellent yield. Reaction of 1‐phenyl‐1‐benzoborole dilithium salt 2 c with MeI yielded the lithium borate 4 c , which is luminescent both in solution and in the solid state.