title: 1,4-Dialkynylbutatrienes: synthesis, stability, and perspectives in the chemistry of carbo-benzenes.
abstract: The π-electron-rich C(8)-conjugated sequence of 1,4-dialkynylbutatrienes is identified as a fragile and fascinating motif occurring in carbo-benzene derivatives, and in Diederich's 1,4-bis(arylethynyl)- or 1,4-bis(triisopropylsilylethynyl)butatriene "capped" representatives, in particular, in tetraalkynylbutatriene. The family of symmetrical 1,4-dialkynylbutatrienes (E-C≡C)RC=C=C=CR(C≡C-E) is extended to functional caps (E=H, CH(3), C≡CPh, CPh=CHBr, or CPh=CBr(2)) with non-alkynyl substituents at the sp(2) vertices (R=Ph or CF(3)). The targets were selected for their potential in appealing retrosynthetic routes to carbo-benzenes, in which the aromatic C(18) macrocycle would be directly generated by sequential metathesis or reductive coupling processes. The functional 1,4-dialkynylbutrienes were synthesized by either classical methods used for the preparation of generic butatrienes (R'Li/CuX-mediated reductive coupling of gem-dihaloenynes or SnCl(2)/HCl-mediated reduction of 3,6-dioxy-octa-1,4,7-triyne precursors). Their spectroscopic and electrochemical properties are compared and analyzed on the basis of the relative extent of total conjugation.
authors: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077 Toulouse, France. vmaraval@lcc-toulouse.fr
authors: Valérie
authors: V
authors: Maraval
authors: Léo
authors: L
authors: Leroyer
authors: Aya
authors: A
authors: Harano
authors: Cécile
authors: C
authors: Barthes
authors: Alix
authors: A
authors: Saquet
authors: Carine
authors: C
authors: Duhayon
authors: Teruo
authors: T
authors: Shinmyozu
authors: Remi
authors: R
authors: Chauvin