Halovinylene Carbonates in Organic Synthesis. New synthetic methods (2)

Abstract

Monohalo‐ and dihalovinylene carbonates constitute a new class of cyclophiles which permit simultaneous introduction of masked α‐hydroxyketo and α‐diketo functions, respectively, into the cycloadducts. Demasking can be performed by simple hydrolysis. Solvolytic opening of the carbonate ring leads to glycolic acid derivatives in the case of the monohalo compounds and to glyoxylic acid derivatives with the dihalo compounds. Preparation of the title compounds, their potential as synthetic reagents, and the chemistry of their simple reaction products are surveyed from a preparative viewpoint.

Four-membered ring compounds containing bis(methylene)cyclobutene or tetrakis(methylene)cyclobutane moieties. Benzocyclobutadiene, benzodicyclobutadiene, biphenylene, and related compounds

“…Although la is sterically ideally set up as a Diels-Alder diene, this type of reaction does not occur, presumably because the ensuing product has to have a cyclobutadiene ring. Addition of diazomethane to la gave the spiro derivatives 37-39.31 '• -^r-37 38 39…”

Radical anions and cations derived from enedithiols, hydroxy-enethiols, and saturated dithiols

“…A second signal grew in very rapidly and had a hyperfine splitting constant of a^ = 2.40 G (8 H). It was originally believed to be that of the 1,4-dlthiane radical cation (63), which is observed when 1,4-dithiane is oxidized by hydroxyl radical (24,25). However, 1,4-dithiane itself in sulfuric acid failed to give an ESR signal.…”