Photosensitized oxygenation of some benzyl sulfides. The role of persulfoxide

✍ Scribed by Sergio M. Bonesi; Mauro Freccero; Angelo Albini

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 77 KB
• Volume: 12
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199909)12:9<703::aid-poc178>3.0.co;2-l

✦ Synopsis

Benzyl ethyl sulfide (6a) is photo-oxidized to benzaldehyde in benzene, whereas diethyl sulfide is known to give inefficiently the sulfoxide under these conditions. Oxidative C-S cleavage is the main process also with benzhydryl ethyl sulfide (6c), but not with a-methylbenzyl ethyl sulfide (6b), which mainly gives the sulfoxide. The carbonyl derivatives reasonably arise from S-hydroperoxy ylides (3). Consistently with this finding, calculations at the PM3 level suggest that the first intermediate, the persulfoxide (1), undergoes intramolecular hydrogen transfer when an activated a-hydrogen is available and gives 3. This is the case for the above benzyl sulfides (DH ≠ for the process decreases with decreasing C-H BDE). However, only some of the persulfoxide conformations are correctly oriented for this rearrangement, and this may slow this process and make other reactions compete, as happens with 6b.