Diazomethane umpolung atop anthracene: An electrophilic methylene transfer reagent

Abstract

Formal addition of diazomethane's terminal nitrogen atom to the 9,10-positions of anthracene yields H[subscript 2]CN[subscript 2]A (1, A = C[subscript 14]H[subscript 10] or anthracene). The synthesis of this hydrazone is reported from Carpino's hydrazine H[subscript 2]N[subscript 2]A through treatment with paraformaldehyde. Compound 1 has been found to be an easy-to-handle solid that does not exhibit dangerous heat or shock sensitivity. Effective umpolung of the diazomethane unit imbues 1 with electrophilicity at the methylene carbon center. Its reactivity with nucleophiles such as H[subscript 2]CPPh[subscript 3] and N-heterocyclic carbenes is exploited for CC bond formation with elimination of dinitrogen and anthracene. Similarly, 1 is demonstrated to deliver methylene to a nucleophilic singlet d[superscript 2] transition metal center, W(ODipp)[subscript 4] (2), to generate the robust methylidene complex [2=CH[subscript 2]]. This behavior is contrasted with that of the Wittig reagent H[subscript 2]CPPh[subscript 3], a more traditional and Brønsted basic methylene source that upon exposure to 2 contrastingly forms the methylidyne salt [MePPh[subscript 3]][2≡CH].]