Stereoselective Cyclopropanation to Homoquinones from Phenacyl Carbenes Obtained through Quinone-Electrogenerated Bases

Abstract

A series of new (E) and (Z)-benzoyl-homoquinones have been prepared in good yield by the parent quinone-electrogenerated base (EGB) in the presence of α-bromoacetophenones or α-bromopropiophenone. The EGB, obtained when electrolysis of p-benzoquinone, or 1,4-naphthoquinone, is carried out at the reduction potential of their first voltammetric peak, conducted to electrogenerated phenacyl carbenes after halide evolution on the first obtained bromo-enolates. The stereoselectivity of the [2 + 2]cycloaddition of the carbene to the quinoid substrate is highly dependent on the electrode nature. Reaction mechanism proposal is discussed.

Facile preparation of 3-substituted 2-quinazolinones via electrogenerated base

“…Moreover radical anions as EGBs have a great potential in organic synthesis, as demonstrated in the stereoselective cyclopropanation to homoquinones from phenacyl carbenes, that we have recently highlighted. 26 Intrigued now by promising further expectation of acetonitrile anion, as strong EGB, in the preparation of many heterocyclic molecules, we focused our attention on using the electrochemistry as a tool to prepare quinazolin-2-one moieties. Herein we report, as outlined in Scheme 1, a novel strategy for the conversion of readily available substrates into 3,4disubstituted quinazolin-2-ones (3) and 4-methylene-3substituted quinazolin-2-ones (4).…”

Organic Electrosynthesis Towards Sustainability: Fundamentals and Greener Methodologies

“…In this case, reaction proceeds via two different quinone‐EGBs (anion radical and dianion) that in the presence of acidic α‐bromoacetophenones or α‐bromopropiophenone conducted to novel bicyclic molecules (Scheme 6). [49] …”