Synthesis of 1,2,3,4-Tetrahydro-1,2-dimethylidenenaphthalene: A Reactive s-cis-Butadiene Undergoing Highly Chemo- and Regioselective Cyclodimerization

✍ Scribed by Elena Roversi; Pierre Vogel; Kurt Schenk

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: German
• Weight: 139 KB
• Volume: 85
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/1522-2675(200205)85:5<1390::aid-hlca1390>3.0.co;2-7

✦ Synopsis

Tetrahydro-1,2-dimethylidenenaphthalene 11 has been derived in three steps from tetralone. In the condensed state and at À 808, it undergoes a highly chemo-and regioselective cyclodimerization to give 3,3',4,4'tetrahydro-2-methylidenespiro[naphthalene-1(2H),2'(1'H)-phenanthrene] ( 14), the structure of which has been established by single-crystal X-ray-diffraction analysis. Dimer 14 undergoes cycloreversion to diene 11 under flash-pyrolysis conditions. The reaction of diene 11 with SO 2 occurs without acid promoter at À 808 and gives a mixture of (AE)-1,4,5,6-tetrahydronaphth[1,2-d][1,2]oxathiin 2-oxide (23; a single sultine), 1,3,4,5-tetrahydronaphtho[1,2-c]thiophene 2,2-dioxide (25), and dimer 14. The high reactivity of diene 1 in its Diels-Alder cyclodimerization and its highly regioselective hetero-Diels-Alder addition with SO 2 can be interpreted in terms of the formation of relatively stable diradical intermediates or by concerted processes with transition states that can be represented as diradicaloids.