title: On ring carbomers of cyclobutane, cyclopentane, and cyclodecane and cyclization reactions through bis(alkynyl-propargyl) coupling.
abstract: A copper-mediated procedure for terminal alkynyl-propargyl coupling has been applied to "skipped" bis-terminal undecatetrayne and 1,4-bis(pseudo)halobut-2-ynes with the aim of preparing ring carbomers of representative strained and loose cycloalkanes, namely [N]pericyclynes. Two unprecedented, cyclic. "skipped" polyynes with CH2 vertices have been isolated as mixtures of diastereoisomers: an isomer 1b and a dimer 2a of [5]pericyclyne 1a. The isomer 1b is a cyclotetrayne with an exocyclic allene function resulting from a unique formal SN process. Its structure has been established by 1H/13C HMQC and HMBC two-dimensional NMR analysis. According to density functional theory calculations, it is about 6 kcalmol(-1) more stable than [5]pericyclyne (1a). Compound 1b can also be regarded as a C13-relaxed [4]pericyclyne, a long sought "skipped" C12 tetrayne. The dimer 2a is a C30 ring that results from a formal SN process. It is a stable ring carbomer of cyclodecane, that is, a [10]pericyclyne, with four CH2 vertices.
authors.affiliation: Laboratoire de Chimie de Coordination, UPR 8241, Toulouse, France. chauvin@lcc-toulouse.fr
authors.forename: L
authors.initials: L
authors.lastname: Maurette
authors.forename: C
authors.initials: C
authors.lastname: Godard
authors.forename: S
authors.initials: S
authors.lastname: Frau
authors.forename: C
authors.initials: C
authors.lastname: Lepetit
authors.forename: M
authors.initials: M
authors.lastname: Soleilhavoup
authors.forename: R
authors.initials: R
authors.lastname: Chauvin