Novel Model Sulfur Compounds as Mechanistic Probes for Enzymatic and Biomimetic Oxidations

Abstract

To test for the intermediacy of sulfide radical cations in biomimetic and enzymatic oxidations, the sulfides PhSCH 3 (1a), PhSCH 2 Ph (1b), PhSCHPh 2 (1c), PhSCPh 3 (1d), CH 3 SCHPh 2 (2), PhSCH 2 CH=CH 2 (3), PhSCH 2 CH=CHPh (4) and CH 3 SCH 2 CH=CHPh (5) were studied, and their results were compared to those obtained for the corresponding chemical electron transfer (CET) and photoinduced electron transfer (PET) oxidations. The radical cations generated from 3−5 by CET in the presence of cerium(IV) ammonium nitrate (CAN) yielded only fragmentation products from the alkyl cations and the thiyl radicals (RS · ), whereas 2 ·+ afforded both fragmentation and mainly α-deprotonation products. Photochemical treatment of the sulfides 1a and 1b with C(NO 2 ) 4 gave only the corresponding sulfoxides, while fragmentation was the main pathway for the photoreactions of 1c, 2 and 5, and for 1d only this latter process was observed. These results support our selection of the sulfides RSCHPh 2 , RSCH 2 CH=CHPh (R = Me, Ph) and PhSCPh 3 as models for the biomimetic and enzymatic studies. As evidenced by the

New Polyphenolic β‐Lactams with Antioxidant Activity

“…, as found in enzymatic and biomimetic oxidations of sulfides to sulfoxides [25]. Even though we could not attempt to identify the products resulting from the reaction between b-lactam 2 and the two radicals, it can be assumed that the S-atom of the thioester is able to act as an electron donor [26], thus conferring antioxidant activity to some extent.…”

(Anthracen-9-yl)methyl sulfides as a mechanistic probe for chemical as well as photochemical electron-transfer reactions

“…CAN has been widely used in organic reactions which include oxidation, [12][13][14][15][16] oxidative addition, [17][18][19][20][21] photooxidation, 22 nitration, [23][24][25] deprotection, 26,27 graft polymerization, 28,29 etc. Intermediates formed in these reactions may undergo oxidative fragmentation, 30,31 rearrangement, [32][33][34] or C-H, C-C and C-S bond [35][36][37][38] cleavages. Organic sulfides can be oxidized with catalytic amounts of Ce(IV) salts rapidly and selectively to sulfoxides.…”

Sulfoxidation on a SiO2-supported Ru complex using O2/aldehyde system

“…8 Neutralization of environmentally toxic sulfides [9][10][11][12][13] and the selective removal of sulfur contents from petroleum feedstock [14][15][16][17] are also important practical applications. Although sulfoxidation is known to proceed in the presence of oxidants (e.g., trifluoroperacetic acid, 18 HNO 3 /H 2 SO 4 solution in nitromethane, 19 iodic acid, 20 and hypervalent iodates [21][22][23] ) without a metal catalyst, the addition of a transition metal source was found to accelerate sulfoxidation using hydrogen peroxide, [24][25][26][27][28] organic peroxide, [29][30][31][32][33][34] NaBrO 3 , 35 PhIO, [36][37][38] NaOCl, 39,40 oxone, 41 or aldehyde/O 2 as oxidants. 16,[42][43][44] Oxidation using O 2 as an oxidant requires harsh reaction conditions and reaction is generally slow, although various metal catalysts have been developed for sulfoxidation using O 2 .…”