The reactions of electrochemical splitting may be successfully used for removal of protecting groups. Theoretical and preparative aspects of the method of electro-deprotection are discussed, and examples of its use are given. The removal often requires high potentials. The use of modified protecting groups (“inner activation”) or of catalysts (electron carriers) which facilitate electron transfer against the standard potential gradient (“external activation”), can greatly increase the scope of the electrochemical method.

Electro‐Deprotection—Electrochemical Removal of Protecting Groups

Whole-cell biooxidation of bromobenzene with Pseudomonas putida 39D or the recombinant Escherichia coli JM109 (pDTG601) yields (1S,2S)-3-bromocyclohexa-3,5-diene-1,2-diol (9a), which is protected as the acetonide and converted to vinylaziridines 7, 15a, 63, and 64. Our route to (+)-pancratistatin features the coupling of a higher order cyanocuprate (derived by ortho-metalation from N,N-dimethyl-2-[(tert-butyldimethylsilyl)oxy]-3,4-(methylenedioxy)benzamide) with aziridine 7 to generate 28, which contains the carbon framework of the title alkaloid. Functional group manipulations resulted in the preparation of epoxydiol 50, which was transformed in a unique fashion and under mild conditions (H2O/PhCO2Na) to (+)-pancratistatin, thus completing a concise synthesis of (+)-pancratistatin in 14 steps from bromobenzene (2% overall yield). To improve this first generation attempt, a new route was devised utilizing carbomethoxyaziridine 64 and its coupling to the cuprate of 3,4-(methylenedioxy)bromobenzene. The add...

Toluene Dioxygenase-Mediated cis-Dihydroxylation of Aromatics in Enantioselective Synthesis. Asymmetric Total Syntheses of Pancratistatin and 7-Deoxypancratistatin, Promising Antitumor Agents1

Chemistry of aliphatic thioether cation radicals and dications

IV. Se−Se, Te−Te, and Mixed Dications 248 V. Trischalcogen Dications 251 VI. Polyatomic Chalcogen Dications 254 A. Preparation 255 B. Chemical Properties 256 VII. N−N Dications 257 A. Hydrazinium Dications 257 1. Synthesis of Hydrazinium Dications 257 2. Properties of Hydrazinium Dications 259 3. Heteroaromatic N,N-Dications 262 B. Diazenium and Diazonium Dications 262 1. Synthesis of Diazenium Dications 262 2. Reactions of Diazenium Dications 263 3. Diazonium Dications 265 4. Mixed Dications 266 VIII. P−P Dications 266 A. Synthesis of Diphosphonium Dications 266 B. Reactions of Diphosphonium Dications: Nucleophilic Substitution 267

1,2-Dications in Organic Main Group Systems

Organic photochemists began to recognize in the 1970sthat a new mechanistic pathway involving excited-state single-electron transfer (SET) could be used to drive unique photochemical reactions. Arnold’s seminal studies demonstrated that SET photochemical reactions proceed by way of ion radical intermediates, the properties of which govern the nature of the ensuing reaction pathways. Thus, in contrast to classical photochemical reactions, SET-promoted excited-state processes are controlled by the nature and rates of secondary reactions of intermediate ion radicals. In this Account, we discuss our work in harnessing SET pathways for photochemical synthesis, focusing on the successful production of macrocyclic polyethers, polythioethers, and polyamides.One major thrust of our studies in SET photochemistry has been to develop new, efficient reactions that can be used for the preparation of important natural and non-natural substances. Our efforts with α-silyl donor-tethered phthalimides and naphthalimides hav...

Studies Leading to the Development of a Single-Electron Transfer (SET) Photochemical Strategy for Syntheses of Macrocyclic Polyethers, Polythioethers, and Polyamides

The anodic oxidation of aliphatic sulfides has been investigated, using cyclic voltammetry and controlled potential electrolysis. Reactions of dimethyl sulfide in acetonitrile have been studied in detail, considering the effects of variation of water content and of type of supporting electrolyte. With as much as 1% water in , dimethyl sulfide is completely oxidized to dimethyl sulfone. In anhydrous , the products are and . It is suggested that the electrochemical reaction involves formation of protons and , which condenses with to form . When perchlorate is present as supporting electrolyte, it is involved in a slow chemical reaction which produces Cl−, , and . The reaction of benzyl methyl sulfide is very similar, leading to benzaldehyde and .

https://iopscience.iop.org/article/10.1149/1.2411587/pdf

Peter T. Cottrell

Papers

Electrochemical Oxidation of Aliphatic Sulfides under Nonaqueous Conditions

Electrochemical reduction of arylsulfonamides

Elektrochemische ox. aliphatischer sulfide unter nichtwaessrigen bedingungen

Elektrochemische red. von 9 arylsulfonamiden