Unusual Fragmentation and Transformation of an N‐Heterocyclic Carbene by a Stable Phosphonium–Borane peri‐Functionalized Naphthalene

Abstract

A 1-phosphonium-8-borane-decorated naphthalene molecule 2 has been found to react with N,N'-dimethylimidazol-2-ylidene (IMe), a popular member of the N-heterocyclic carbene (NHC) family, which converts it into two vinyl-amine fragments one of which is trapped between the phosphonium and borane unit by the formation of a C-C and a B-N bond. The same reactivity was not observed for larger NHC molecules. Control experiments and mechanistic studies have established the involvement of an ylide-borane molecule and an imidazolium salt in addition to IMe carbene in this new transformation of an NHC.

1,8‐Diarylnaphthalenes: Synthesis, Properties, and Applications

“…The above synthetic approach was also applied to synthesize 1,8-diarylnaphthalene 139, which is a phosphine-borane Lewis pair (Scheme 44). [82,83] Compound 139, despite being sterically crowded, was able to convert to phosphonium salt 140 and to form 2 : 1 complexes with Au(I) and Pt(II) 141. In compound 139, an intense P!B charge transfer and a bright solvent-dependent double emission switched by fluorine ions were observed.…”

“…It was also noted that the P−B type Lewis pairs gave a greater response to fluorine ions than the N−B analogs described above. The ability of phosphonium salt 140 to fragment N‐heterocyclic carbenes was reported [83] …”

“…The ability of phosphonium salt 140 to fragment N-heterocyclic carbenes was reported. [83] Arylation of 1,8-diiodonaphthalene 7 via successive Negishi and Suzuki reactions was used to synthesize porphyrin derivative 144 (Scheme 45). [84][85][86] The latter was converted to quinone 145 by treatment with boron tribromide in benzene followed by aqueous Na 2 CO 3 .…”