Reactions of Cyclic Diynes with Acceptor‐Substituted Alkynes: Syntheses of Doubly Bridged Dewar Benzenes

Abstract

The reaction of the AlC13 complex of cyclic diynes (mainly a 14-membered ring) with dimethyl acetylenedicarboxylate (DMAD) or bis(tert-butylsulfony1)acetylene (BTSA) and related compounds was investigated. The reaction of the A1C13 complex of cyclotetradeca-1,8-diyne (1, n = 5 ) with DMAD affords in 60% yield two isomers in a ratio of 7:3. The isomers were identified as the 1,4-and 2,3-bridged Dewar benzene derivative A and the 1,2-and 3,4-bridged Dewar benzene derivative B. Acetylenes with sterically more demanding groups such as BTSA or bis(diphenylphosphany1)acetylene P,P'-dioxide (BDPA) yield only the isomer A. The X-ray structures of the cycloadduct between 1 (n = 5 and 6) and BTSA, as well as of 2,3-bis(tert-butylsuIfonyl)-1,4,5,6-tetramethylbicyclo[2.2.0]hexa-2,5-diene (31) are described. The mechanism of the cycloadditions is discussed.

Alkynes Between Main Group Elements: From Dumbbells via Rods to Squares and Tubes

“…Pericàs and co-workers found a procedure yielding quantitatively the desired product 382 by oxidizing bis( t -butylthio)acetylene ( 381 ) with m CPBA in chloroform (Scheme ) . Bis( t -butylsulfonyl)acetylene, the structural properties of which could even be elucidated by X-ray analysis, was widely used as a highly reactive dienophile in Diels−Alder reactions ,− and as alkyne component in highly electrophilic CpCo(monoalkyne) complexes. − Also bis(arylsulfonyl)acetylenes 385 and 386 were synthesized; however, a neutral oxidizing agent, such as dimethyldioxirane (DMDO), was necessary to achieve high yields (Scheme ); the corresponding products 385 and 386 could not be isolated without decomposition …”

Bis(tert-butylsulfonyl)ethyne and 1-tert-butylsulfinyl-2-tert-butylsulfonylethyne

“…The high reactivity of bis(tert-butylsulfonyl)ethyne, (I), as a dienophile in Diels±Alder reactions has been demonstrated in several reports (Riera et al, 1990;Virgili et al, 1991;Gleiter & Ohlbach, 1994;Gleiter et al, 1996). Compound (I) is the only known stable ethyne substituted by two sulfonyl groups, whereas bis(arylsulfonyl)ethynes are reported as unstable at room temperature (Pasquato et al, 1991).…”

Cycloadditions and Cyclizations of Acetylenic, Allenic, and Conjugated Dienyl Sulfones

“…A subsequent photochemical variation was also reported . Gleiter et al employed aluminum trichloride as the Lewis acid to synthesize Dewar benzenes and bridged prismanes from the cyclization of the doubly activated acetylenic sulfone 38 with a series of macrocyclic diynes. The sulfonyl substituents were further subjected to reductive desulfonylation with samarium iodide or substitution with organolithium or Grignard reagents (Scheme ).…”