Photochemical fragmentation of 4-alkylpyrimidines and 2-alkylquinolines

✍ Scribed by Sreedharan Prathapan; Sarah Loft; William C. Agosta

• Publisher: Elsevier Science
• Year: 1988
• Tongue: French
• Weight: 187 KB
• Volume: 29
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)88458-0

✦ Synopsis

Hydrogen abstraction and fragmentation occur on acetone-sensitized photolysis of 4alkylpyrimidines la-c with formation of 4-methylpyrimidine (2); the selectivity for primary, secondary, and tertiary hydrogen transfer is considerably greater in la-c than in Z-alkylquinolines 7a-c.

We have found that hydrogen transfer and fragmentation occur on acetone-sensitized population of the first triplet state (mr *) of the 4-alkylpyrimidines la-c (eq 1). Direct irradiation of pyrimidines la-c, which were prepared following a known procedure,'s2 in benzene or tert-butyl alcohol as solvent, using a medium-pressure mercury arc lamp and either a potassium chromate solution (x -313 mn) or Pyrex glass (A >280 nm) as a filter, led to no reaction and recovery of starting pyrimidine. Irradiation in acetone (E, -79-82 kcal/mo13) as solvent through Pyrex, however, led to slow destruction of starting material and as R, = Ra = CHJ; b, R, = CHa, R2 = H; o, R,