Intramolecular carbenoid insertions into thiophene: Reactions of 1-diazo-3-(2-thienyl)-2-propanone and 1-diazo-3-(3-thienyl)-2-propanone

✍ Scribed by Christopher S. Frampton; David L. Pole; Kelvin Yong; Alfredo Capretta

• Book ID: 104257487
• Publisher: Elsevier Science
• Year: 1997
• Tongue: French
• Weight: 262 KB
• Volume: 38
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(97)01131-3

✦ Synopsis

Treatment of 1-diazo-3-(2-thienyl)-2-propanone with catalytic rhodium (II) acetate results in cyclopropanation followed by acid-catalyzed ring opening and tautomerization to yield 5,6-dihydro-4Hcyclopenta[b]thiophen-5-one. Under the same conditions, however, the isomeric l-diazo-3-(3-thienyl)-2propanone generates a cyclopropane intermediate which undergoes [4+2] eyeloreversion, isomerization and Diels-Alder dimerization to give a complex spiro-disulphide. While the 2-substituted thiophene behaves like other homologous members of the thienyl series, the isomeric 3-substituted thiophene undergoes chemistry seen previously with analogous furanyl compounds. The insight into the mechanistic underpinnings provided by preliminary molecular modeling at a PM3 level is discussed.