Photochemical Desulfonylation ofN-Tosyl Amides by 2-Phenyl-N,N′-­Dimethylbenzimidazoline (PDMBI)

Abstract

Photoinduced electron transfer reaction between N-tosyl amides and 2-phenyl-N,N¢-dimethylbenzimidazoline (PDMBI) provides an efficient approach for the desulfonylation of N-tosyl amides.

One‐Pot Multicomponent Synthesis of β‐Amino Amides

“…The scalability of this method was also investigated, and a 5 mmol scale reaction of 1 a , 2 a , 3 a and 4 a yielded 1.74 g of product 5 a (68 % yield). N‐Detosylation of 5 a was easily realized by utilizing photochemical desulfonylation in the presence of reductive 2‐phenyl‐ N , N ′‐dimethylbenzimidazoline (PDMBI) to afford β‐peptidic peptidomimetics 5 q′ , further demonstrating the synthetic utility …”

“…N-Detosylation of 5 a was easily realized by utilizing photochemical desulfonylation in the presence of reductive 2-phenyl-N,N'-dimethylbenzimidazoline (PDMBI) to afford b-peptidic peptidomimetics 5 q', further demonstrating the synthetic utility. [14] To gain insight into the reaction mechanism, an isotope labeling reaction was conducted (Scheme 3). O 18 -labeled benzoic acid [O 18 ]-3 a was initially treated with ynamide 4 a to give the benzoyloxyenamide intermediate 6, which was subjected to the MCR with 1 a and 2 a and delivered labeled bamino amide [O 18 ]-5 a.…”

“…Initially we carried out the reaction by mixing 3 a and 4 a in DCM at room temperature under argon to form the enamide intermediate, then added 1 a and 2 a to trap the enamide, and no new product was observed ( [10][11][12][13][14], and only ZnCl 2 lead to the formation of 5 a in 11 % yield. Finally, when DCE was used as solvent, the yield decreased to 35 % (entry 15).…”

One‐Pot Multicomponent Synthesis of β‐Amino Amides

“…N-Detosylation of 5a was easily realized by utilizing photochemical desulfonylation in the presence of reductive 2-phenyl-N,N'-dimethylbenzimidazoline (PDMBI) to afford b-peptidic peptidomimetics 5q' ', further demonstrating the synthetic utility. [14] To gain insight into the reaction mechanism, an isotope labeling reaction was conducted (Scheme 3). Based on these results and the literature, [5] ap lausible reaction mechanism is proposed in Figure 1.…”

Transition-Metal-Free and Visible-Light-Mediated Desulfonylation and Dehalogenation Reactions: Hantzsch Ester Anion as Electron and Hydrogen Atom Donor

“…49 The PET process under UV irradiation using 2-phenyl-N,N′dimethylbenzimidazoline as electron and hydrogen donor has been used in tosyl amide deprotection. 50 N-sulfonyl indoles can be deprotected by a PET reaction with NEt 3 serving as both an electron and proton donor and n-Bu 3 SnH serving as a hydrogen atom donor. 51 In 2013, Xiao et al reported Ndetosylation of tosyl amides using visible light and iridium as photocatalysts with Hantzsch ester (HE, diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate) as electron donor.…”