Diverse Reactivity of Diazatitanacyclohexenes: Coupling Reactions of 2 H-Azirines Mediated by Titanium(II)

Addison N. Desnoyer, Xin Yi See, Ian A. Tonks

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

2H-Azirines are versatile coupling partners for the synthesis of N-heterocycles. Herein, we present our studies on the reactivity of Cp2Ti(BTMSA) (1; BTMSA = bis(trimethylsilyl)acetylene) with a variety of azirines. In all the cases examined, the initial organometallic products formed are diazatitanacyclohexenes, presumably formed via oxidative addition of Ti(II) into the C-N bond of the azirine to form an azatitanacyclobutene intermediate, followed by C=N insertion of a second equivalent of azirine into the Ti-C bond to form the observed products. Diazatitanacyclohexene 3, bearing phenyl substituents and derived from 2,3-diphenyl-2H-azirine, fragments to form an azabutadiene and nitrile, which is shown to be catalytic in the presence of excess 2,3-diphenyl-2H-azirine. H-substituted complex 8, derived from 3-phenyl-2H-azirine, decomposes via protonolysis of the Cp ligands. In contrast, the methyl-substituted diazatitanacyclohexene 10, derived from 2-methyl-3-phenyl-2H-azirine, is thermally robust. Attempts to trap the putative azatitanacyclobutene intermediate with an alkyne were unsuccessful, resulting instead in the formation of titanacyclopentadiene (12) from coupling of alkyne with BTMSA. Initial reactivity studies found that 10 could be protonolyzed with AcOH to form mixtures of pyrrole and aziridine products, whereas reacting 10 with MeOH results solely in the formation of 2,4-dimethyl-3,5-diphenyl-1H-pyrrole.

Original languageEnglish (US)
Pages (from-to)4327-4331
Number of pages5
JournalOrganometallics
Volume37
Issue number23
DOIs
StatePublished - Dec 10 2018

Bibliographical note

Funding Information:
Financial support was provided by the National Institutes of Health (1R35GM119457) and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Equipment for the Chemistry Department NMR facility was supported through a grant from the National Institutes of Health (S10OD011952) with matching funds from the University of Minnesota.

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