Cycloaromatization and cyclodimerization of bridged diallenes

✍ Scribed by S. Braverman; Y. Duar; D. Segev

• Book ID: 104226146
• Publisher: Elsevier Science
• Year: 1976
• Tongue: French
• Weight: 262 KB
• Volume: 17
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)93874-7

✦ Synopsis

Recently, we have shown that bis-y,y-dimethylallenyl sulfone (J) undergoes a novel and facile cyclization on heating at 75O to 3-isopropcnyl-4-isopropylthiophene l,l-dioxide (2)2. The reaction mechanism may either involve a 2,2 '-bisallyl-type biradical intermediate or may be described as a concerted intramolecular ene reaction 2 . As a natural extension of this work, we decided to investigate the cyclization of various diallenic systems, especially those capable to undergo simultaneous aromatization. And as one of the moat suitable candidates for such an extension, we have chosen the sulfide analog of 1, compound 2, which on cyclisation should lead to tbiophene 4. However, while the diallenic sulfone 1, can be obtained very conveniently by a double 12,31-sigmatropic rearrangment of bis-a,a-dirnethyl-propargyl sulfoxylate, it is difficult to synthesize the diallenic sulfide 3, as well as