This communication describes the Pd(OAc)2-catalyzed intermolecular amidation reactions of unactivated sp2 and sp3 C-H bonds using primary amides and potassium persulfate. The substrates containing a pendent oxime or pyridine group were amidated with excellent chemo- and regioselectivities. It is noteworthy that reactive C-X bonds were well-tolerated and a variety of primary amides can be effective nucleophiles for the Pd-catalyzed C-H amidation reactions. For the reaction of unactivated sp3 C-H bonds, beta-amidation of 1 degrees sp3 C-H bonds versus 2 degrees C-H bonds is preferred. The catalytic reaction is initiated by chelation-assisted cyclopalladation involving C-H bond activation. Preliminary mechanistic study suggested that the persulfate oxidation of primary amides should generate reactive nitrene species, which then reacted with the cyclopalladated complex.

Direct functionalization of CÀH bonds is an appealing strategy in organic synthesis [1] but its practical application has so far been difficult to realize. The selective functionalization of primary C À H bonds of alkanes that also contain secondary and/or tertiary C À H bonds is a great challenge, as CÀH bond energy follows an order primary > secondary > tertiary. [1c,d] In seminal works by Bergman, [1b] Jones, [1c] and their respective co-workers, stoichiometric reactions of alkanes with [Cp*(Me 3 P)M] (Cp* = C 5 Me 5 ; M = Rh, Ir) resulted in the formation of C À M bonds by selective activation of primary C À H bonds. Subsequent work by Hartwig and coworkers [1g,i, 2] demonstrated C À B bond formation by stoichiometric and catalytic functionalization of primary CÀH bonds mediated by tungsten, rhodium, or ruthenium complexes. The high selectivity for primary CÀH bond functionalization in these C À M or C À B bond-formation reactions (Scheme S1 in the Supporting Information) is considered to result from kinetic factors or steric interaction between the metal complexes and alkanes. [1i, 3] A well-established process in CÀC bond formation by direct CÀH bond functionalization is the metal-catalyzed intra-and intermolecular carbenoid insertion into C À H bonds, with diazo compounds as the carbene source. [1o, 4] These catalytic C À C bond-formation reactions generally feature lower selectivity for primary CÀH bonds than for secondary and tertiary CÀH bonds. For example, a selectivity order of primary < secondary < tertiary C À H bonds has been observed for the extensively investigated carbene insertion catalyzed by rhodium complexes, [4,5] possibly because of the electron density order of primary < secondary < tertiary CÀH bonds, which renders primary CÀH bonds the least susceptible to attack by electrophilic rhodium-carbene intermediates.[5] By manipulating the steric or electronic properties of the metal catalysts, a selectivity for primary C À H bonds of alkanes comparable to that for secondary or tertiary C À H bonds was observed, [6] with the highest primary/secondary and primary/tertiary ratio per CÀH bond being 1.17:1.0[6b] and 1.0:0.9, [6c] respectively. Herein we report a highly selective primary CÀH bond functionalization by metal-catalyzed carbenoid insertion into the C À H bonds of alkanes (Scheme 1), which features a primary/secondary selectivity (that is, the primary/secondary ratio per C À H bond) of up to 11.4:1. We have also accomplished highly enantioselective functionalization of secondary C À H bonds with ee values of up to 93 % and product turnovers up to 6100 through metal-mediated carbenoid CÀH bond insertion reactions.Our studies in this work were inspired by previous work from the research groups of Callot [6a,b] and Suslick. [7] In the 1980s, Callot and co-workers reported that the primary C À H bond selectivity for the reaction of linear alkanes with ethyl diazoacetate (N 2 CHCO 2 Et, EDA) catalyzed by [Rh(por)I] (H 2 (por) = meso-tetraarylporphyrin) increases with the size o...

Catalytic oxidation of 1‐alkenes to aldehydes by an epoxidation–isomerization pathway with air or dioxygen as terminal oxidant has been realized for bulky ruthenium(VI) porphyrin catalysts. For the new, recyclable catalyst [RuVI(tmttp)O2], product yields of up to 99 % and total turnover numbers of up to 1144 were obtained.

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Catalytic oxidation of 1‐alkenes to aldehydes by an epoxidation–isomerization pathway with air or dioxygen as terminal oxidant has been realized for bulky ruthenium(VI) porphyrin catalysts. For the new, recyclable catalyst [RuVI(tmttp)O2], product yields of up to 99 % and total turnover numbers of up to 1144 were obtained.

Direct functionalization of CÀH bonds is an appealing strategy in organic synthesis [1] but its practical application has so far been difficult to realize. The selective functionalization of primary C À H bonds of alkanes that also contain secondary and/or tertiary C À H bonds is a great challenge, as CÀH bond energy follows an order primary > secondary > tertiary. [1c,d] In seminal works by Bergman, [1b] Jones, [1c] and their respective co-workers, stoichiometric reactions of alkanes with [Cp*(Me 3 P)M] (Cp* = C 5 Me 5 ; M = Rh, Ir) resulted in the formation of C À M bonds by selective activation of primary C À H bonds. Subsequent work by Hartwig and coworkers [1g,i, 2] demonstrated C À B bond formation by stoichiometric and catalytic functionalization of primary CÀH bonds mediated by tungsten, rhodium, or ruthenium complexes. The high selectivity for primary CÀH bond functionalization in these C À M or C À B bond-formation reactions (Scheme S1 in the Supporting Information) is considered to result from kinetic factors or steric interaction between the metal complexes and alkanes. [1i, 3] A well-established process in CÀC bond formation by direct CÀH bond functionalization is the metal-catalyzed intra-and intermolecular carbenoid insertion into C À H bonds, with diazo compounds as the carbene source. [1o, 4] These catalytic C À C bond-formation reactions generally feature lower selectivity for primary CÀH bonds than for secondary and tertiary CÀH bonds. For example, a selectivity order of primary < secondary < tertiary C À H bonds has been observed for the extensively investigated carbene insertion catalyzed by rhodium complexes, [4,5] possibly because of the electron density order of primary < secondary < tertiary CÀH bonds, which renders primary CÀH bonds the least susceptible to attack by electrophilic rhodium-carbene intermediates. [5] By manipulating the steric or electronic properties of the metal catalysts, a selectivity for primary C À H bonds of alkanes comparable to that for secondary or tertiary C À H bonds was observed, [6] with the highest primary/secondary and primary/tertiary ratio per CÀH bond being 1.17:1.0 [6b] and 1.0:0.9, [6c] respectively.Herein we report a highly selective primary CÀH bond functionalization by metal-catalyzed carbenoid insertion into the C À H bonds of alkanes (Scheme 1), which features a primary/secondary selectivity (that is, the primary/secondary ratio per C À H bond) of up to 11.4:1. We have also accomplished highly enantioselective functionalization of secondary C À H bonds with ee values of up to 93 % and product turnovers up to 6100 through metal-mediated carbenoid CÀH bond insertion reactions.Our studies in this work were inspired by previous work from the research groups of Callot [6a,b] and Suslick. [7] In the 1980s, Callot and co-workers reported that the primary C À H bond selectivity for the reaction of linear alkanes with ethyl diazoacetate (N 2 CHCO 2 Et, EDA) catalyzed by [Rh(por)I] (H 2 (por) = meso-tetraarylporphyrin) increases with the size of...

Stereoselective Intramolecular Carbene C-H Insertion Catalyzed by Rhodium(III) Porphyrin Complexes. -Among some Rh(III)-porphyrin complexes tested, (I) is found to be the most efficient catalyst for the intramolecular carbene C-H insertion of α-diazoacetamides to form βor γ-lactams with high diastereoselectivity. -(LO, V. K.-Y.; THU, H.-Y.; CHAN, Y.-M.; LAM, T.-L.; YU, W.-Y.; CHE*, C.-M.; Synlett 2012, 19, 2753-2757, http://dx.

Enantioselective C-C Bond Formation. -A Rh-complex of bis-pocket porphyrin catalyzes carbenoid insertion into CH bonds of n-alkanes with high primary/secondary selectivity. Enantioselective secondary CH-bond functionalization catalyzed by a Rh complex of Halterman's chiral porphyrin features up to 93% e.