Allylic C-H amination

Zhu and Chiba applied a TEMPO-mediated allylic C—H amination involving alkenyl hydrazones to the synthesis of tetrahydropyridazines 8 and dihydrophthalazines 9 (Scheme 5) (140BC4567). Optimal reaction conditions were found to be treatment of the respective hydrazone with 3 equivalents of TEMPO in A/,N-dimethylformamide (DMF) at 130°C, giving the corresponding products in moderate-to-high yields. 

A theoretical approach to understanding the nature of intramolecular allylic C-H amination versus alkene aziridination reaction pathways was presented, where the reaction of 4-pentenylsulfamate 192 was investigated using three different dirhodium catalysts (14JOC9799). The 1/A ratios of products for the three catalysts range from 1 4 to 1 1 to >20 1 and the theoretical observations presented are consistent with experimental results. 

Scheme 58 Selective intramolecular allylic C-H amination catalyzed by 106...

In fact, the stepwise nature of [Ru2(hp)4Cl] catalyzed reaction accounts for preferential allylic C-H bond functionalization over alkene aziridination which is the favored product when dirhodium catalysts are used. The presence of a discrete diradical intermediate further assists the selectivity for allylic C-H amination using a diruthenium catalyst. 

Scheme 8.3 Selective Ru -catalyzed intramolecular allylic C-H amination. (Adapted from Ref. [111].)...

This approach has also been leveraged toward the construction of differentiated imidazolidinone and aminooxazoline structures. Tandem approaches toward allylic C—H amination and sequential arylation have been demonstrated to access functionalized oxazolidinones toward homophenylalanine derivatives directly from the linear alkenyl carbamate (Scheme 3.22)."°... 

SCHEME 3.22 Sequential allylic C—H amination/vinylic arylation. 

Reed and White provided a rare example of an inter-molecular linear allylic C—H amination (LAA) using a heterobimetallic catalysts in which one of the catalysts was cobalt-based. " Treatment of allylcyclohexane 267 with A-(methoxycarbonyl)-p-toluenesulfonamide in the presence of commercially available catalysts bis-sulfoxide/Pd(OAc)2 and (salen)Co(III)OAc, benzoquinone (BQ) and tert-butyl methyl ether (TBME) gave the desired linear E-allylic amine 268 in 17% yield with... 

Paradine SM, White MC. Iron-catalyzed intramolecular allylic C-H amination. J Am Chem Soc. 2012 134 2036-2039. 

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