Palladium-Catalyzed Diamination of Olefins

Key words

palladium - olefin diamination - C-H activation

Significance

Complementary to previous approaches to diaminate olefins and as an extension to the group’s previous work in the area (H. Du, B. Zhao, Y. Shi J. Am. Chem. Soc. 2007, 129, 762), terminal olefins were diaminated at allylic and homoallylic carbons by a Pd-catalyzed C-H insertion under solvent-free conditions. The nitrogen source is di-tert-butyldiaziridinone, which can be synthesized in a few steps. The scope encompasses both monosubstituted and 1,1-disubstituted terminal olefins, and the resulting products can be converted into the free diamine by treatment with TFA and concentrated acid. Diamination is also possible, with 1,9-decadiene producing a 1:1 mixture of diastereomers and with 1,7-octadiene producing a single diastereomer.

Comment

Diamination of olefins is a potentially efficient strategy for synthesizing vicinal diamines. The present method needs to be solvent-free and have slow addition of the nitrogen source. The diamination results for 1,9-decadiene versus 1,7-octa­diene suggest that the first diamination influences the stereochemical outcome of the second di­amination unless the two olefins are too far apart. Although the exact mechanism is unknown, intermediates A and B have been isolated and both shown to lead to the product, which suggests that a conjugated diene is formed after the first di­amination. The authors also speculate that Pd(0) inserts into the N-N bond of the diaziridinone, followed by coordination with the olefin, π-allyl formation, and nucleophilic attack of the amine moieties onto the olefin to furnish the product. A means of producing differentially protected diamines would be very attractive.