The discovery, study, and implementation of the Co- and Mn-catalyzed hydrohydrazination and hydroazidation reactions of olefins are reported. These reactions are equivalent to direct hydroaminations of C-C double bonds with protected hydrazines or hydrazoic acid but are based on a different concept in which the H and the N atoms come from two different reagents, a silane and an oxidizing nitrogen source (azodicarboxylate or sulfonyl azide). The hydrohydrazination reaction using di-tert-butyl azodicarboxylate is characterized by its ease of use, large functional group tolerance, and broad scope, including mono-, di-, tri-, and tetrasubstituted olefins. Key to the development of the hydroazidation reaction was the use of sulfonyl azides as nitrogen sources and the activating effect of tert-butyl hydroperoxide. The reaction was found to be efficient for the functionalization of mono-, di-, and trisubstituted olefins, and only a few functional groups are not tolerated. The alkyl azides obtained are versatile intermediates and can be transformed to the free amines or triazoles without isolation of the azides. Preliminary mechanistic investigations suggest a rate-limiting hydrocobaltation of the alkene, followed by an amination reaction. Radical intermediates cannot be ruled out and may be involved.

Conversion of olefins to azides was achieved with high Markovnikov selectivity for a broad range of alkenes using 6 mol % Co(BF4).6H2O and ligand 1, with 3 equiv of TsN3 as nitrogen source and simple silanes (PhSiH3, TMDSO).

A novel sulfenylation method induced by aromatization of quinone mono-O,S-acetals is described. These sulfenylation reagents readily react with silyl enolethers or electron rich aromatic compounds to give sulfenylation products under mild conditions. In particular, O,S-acetal 2j, which possesses a pentafluorophenylthio function, is the most effective reagent from the standpoint of the adaptability for various substrates.

As a result of enormous ring strain, cyclopropene compounds display a range of diverse reactivities in both noncatalytic and transition-metal-catalyzed transformations, thus presenting unique opportunities for organic synthesis. [1,2] To further enhance the synthetic potential of cyclopropenes, the development of expeditious methods for the synthesis of enantioenriched cyclopropenes is highly desirable.[3] In this context, a cyclopropenation reaction of alkynes with diazo compounds that is catalyzed by chiral dirhodium(II) complexes represents one of the most powerful means for the construction of this class of optically active building blocks. Doyle, Müller, and co-workers were the first to demonstrate asymmetric induction (up to ! 98 % ee) in cyclopropenation reactions of terminal alkynes including propargyl alcohol or propargylamine derivatives with diazoacetates using [Rh 2 (5S-mepy) 4 ] (2 a; Scheme 1) as a chiral catalyst.[4] Doyle et al. also reported an enantioselective intramolecular cyclopropenation of diazoacetates, in which [Rh 2 (4S-ibaz) 4 ] (2 b) provided macrocyclic cyclopropenes in up to ! 99 % ee.[5] Corey and coworkers demonstrated that a new mixed carboxylate/carboxamidate catalyst [Rh 2 (OAc)(dpti) 3 ] (3) is highly exceptional for cyclopropenation of a broad range of terminal alkynes with ethyl diazoacetate.[6] The extension of this methodology to include a-substituted a-diazoacetates is particularly attractive because it has the capability to form cyclopropenes with a quaternary stereogenic carbon center. [7][8][9] Although high levels of enantioselectivity (up to 99 % ee) in cyclopropenations of terminal alkynes with aryldiazoacetates [7a] or arylvinyldiazoacetates [7b] under catalysis by [Rh 2 (S-dosp) 4 ] (4) have been reported by Davies and co-workers, the goal for the reaction with a-alkyl-a-diazoesters remains elusive because of the propensity to form a,b-unsaturated esters through a 1,2-hydride shift.[10] Panne and Fox recently disclosed that dirhodium(II) tetrapivalate exhibits high selectivity for cyclopropenation over alkene formation in the reaction of terminal alkynes with a-alkyl-a-diazoesters. [11,12] However, to the best of our knowledge, an enantioselective version of this reaction has not been reported.Our research group has previously demonstrated the first examples of highly enantio-, diastereo-, and chemoselective intramolecular C À H insertion reactions of a-alkyl-a-diazoesters by using dirhodium(II) tetrakis[N-phthaloyl-(S)-tertleucinate] ([Rh 2 (S-pttl) 4 ], 1 a) in which high levels of asymmetric induction (up to 95 % ee) were achieved. [13][14][15] Herein, we report that [Rh 2 (S-tbpttl) 4 ] (1 f), a new dirhodium(II) carboxylate complex that incorporates N-tetrabromophthaloyl-(S)-tert-leucinate as chiral bridging ligands, catalyzes the cyclopropenation reaction of terminal alkynes with 2,4-dimethyl-3-pentyl a-alkyl-a-diazoacetates to give 1,2-disubstituted 2-cyclopropenecarboxylates in good to high yields and with up to 99 % ee. Scheme 1. Chiral dirhodium(II) com...