Catalytic, Enantioselective syn-Diamination of Alkenes

Abstract

The enantioselective, vicinal diamination of alkenes represents one of the stereocontrolled additions that remains an outstanding challenge in organic synthesis. A general solution to this problem would enable the efficient and selective preparation of widely useful, enantioenriched diamines for applications in medicinal chemistry and catalysis. In this article, we describe the first enantioselective, syn-diamination of simple alkenes mediated by a chiral, enantioenriched organoselenium catalyst together with a N,N′-bistosyl urea as the bifunctional nucleophile and Nfluorocollidinium tetrafluoroborate as the stoichiometric oxidant. Diaryl, aryl-alkyl, and alkylalkyl olefins bearing a variety of substituents are all diaminated in consistently high enantioselectivities but variable yields. The reaction likely proceeds through a Se(II)/Se(IV) redox catalytic cycle reminiscent of the syn-dichlorination reported previously. Furthermore, the synstereospecificity of the transformation shows promise for highly enantioselective diaminations of alkenes with no strong steric or electronic bias.

Insights into the Recent Synthetic Advances of Organoselenium Compounds

“…However, its extension towards diamination of alkenes has not been fruitful for the chemists. [146] Recently, Denmark et al, [147] have achieved catalytic, enantioselective syn-diamination of alkenes 72 in the presence of chiral, enantioenriched diselenide 74, originally developed for syn-dichlorination as previously discussed, mediating through a Se II /Se IV redox cycle with the use of stronger bifunctional nucleophile 71. The reaction protocol was optimized for 4phenyl-1-butene 72 (R 1 = (CH 2 ) 2 Ph, R 2 = H) as model substrate after detailed screening of diselenide precursors, bases, oxidants and solvents employed to afford the best possible results with good yields and enantioselectivities (Scheme 31).…”

Catalytic, Enantioselective Diamination of Alkenes

“…38 Inspired by their previous work on organoselenium-catalyzed syn-dichlorination of alkenes, 39 Denmark and co-workers disclosed a chiral, organoselenium-catalyzed, enantioselective diamination of alkenes with easily accessible N,N′-bistosyl urea as the diamination agent (Scheme 16). 40 The use of N-fluorocollidinium tetrafluoroborate as the final oxidant is critical to the success of this transformation. A variety of trans-alkenes, including internal styrenes, diaryl and diakyl alkenes, react smoothly in this reaction, yielding the diamination products in variable yields with consistently excellent diastereo-and enantioselectivities.…”

“…As illustrated in Scheme 17 40 the catalytic cycle is initiated by organoselenium(II) species Int-19, which is generated by oxidation of the diaryl diselenide catalyst. The electrophilic species Int-19 can react with an alkene to form the active seleniranium ion intermediate Int-20, which is opened by the urea nucleophile under basic conditions to deliver Int-21.…”

Iron‐Catalyzed Radical Asymmetric Aminoazidation and Diazidation of Styrenes

“…While C−C bond formation involving reductive coupling of aldimines [2] and/or imines [3] is effective for the synthesis of chiral diamines, the catalytic asymmetric diamination of alkenes or dienes is the most straightforward and convenient approach to production of these structures (Scheme 1). Shi, [1d, 4] Du, [5] Gong, [6] Muñiz [7] and Denmark [8] have established powerful palladium‐, aryliodine‐ and organoselenium‐catalyzed intermolecular diamination of alkenes or dienes, respectively. Michael, [9] Chemler, [10] Zeng [11] and Liu [12] developed palladium or copper catalyzed inter/intramolecular diamination with one external amination reagent and the other derived from alkene substrates, producing useful chiral indolines and pyrrolidines.…”