Ti-Catalyzed Modular Ketone Synthesis from Carboxylic Derivatives and gem-Dihaloalkanes.

Ketones are ubiquitous in organic synthesis. However, the general method to convert widely available carboxylic acids, unactivated esters, and amides into ketones remains elusive. Herein, we describe the Ti-catalyzed modular ketone synthesis from carboxylic derivatives and easily accessed gem-dihaloalkanes. Notably, this protocol could achieve the direct catalytic olefination of carboxylic acids. This method features a sequence of olefination and electrophilic transformation and good functional group compatibility and allows rapid access to various functionalized ketones. Preliminary mechanistic studies provide insights into the reaction pathway and support the intermediacy of plausible alkylidene titanocene and gem-bimetallic complexes.

Ti-Catalyzed Diastereoselective Cyclopropanation of Carboxylic Derivatives with Terminal Olefins.

Cyclopropanols and cyclopropylamines not only serve as important structural motifs in medicinal chemistry but also show diverse reactivities in organic synthesis. Owing to the high ring strain energy, the development of a general protocol from stable and readily available starting materials to afford these cyclopropyl derivatives remains a compelling challenge. Herein, we describe that a Ti-based catalyst can effectively promote the diastereoselective syntheses of cyclopropanols and cyclopropylamines from widely accessible carboxylic derivatives (acids, esters, amides) with terminal olefins. To the best of our knowledge, this method represents the first example of direct converting alkyl carboxylic acids into cyclopropanols. Distinct from conventional studies in Ti-mediated cyclopropanations with reactive alkyl Grignard reagents as nucleophiles or reductants, this protocol utilizes Mg and Me2SiCl2 to turn over the Ti catalyst. Our method exhibits broad substrate scope with good functional group compatibility and is amenable to late-stage synthetic manipulations of natural products and biologically active molecules.

Palladium-Catalyzed Ring-Opening Coupling of gem-Difluorocyclopropanes for the Construction of 2-Fluoroallylic Sulfones.

A Pd-catalyzed ring-opening sulfonylation of gem-difluorocyclopropanes is reported. This protocol involves C-C bond cleavage, ß-F elimination, and allylic coupling to form corresponding 2-fluoroallylic sulfones efficiently with Z-selectivity. Different substrates bearing diverse functional groups are tolerated. Moreover, this method is successfully used for the late-stage derivation of several bioactive molecules.

Cu-Mediated Sulfonyl Radical-Enabled 5- exo-trig Cyclization of Alkenyl Aldehydes: Access to Sulfonylmethyl 1 H-Indenes.

An efficient method for the construction of sulfonylmethyl 1 H-indenes via Cu(I)-mediated sulfonyl radical-enabled 5- exo-trig cyclization of alkenyl aldehydes has been developed for the first time. Mechanistic studies indicated that a radical addition-cyclization-elimination (RACE) process might be involved. The reaction features a relatively broad substrate scope, good annulation efficiency, and varying functional group tolerance.

Meta-Selective CAr-H Nitration of Arenes through a Ru3(CO)12-Catalyzed Ortho-Metalation Strategy.

The first example of transition metal-catalyzed meta-selective CAr-H nitration of arenes is described. With the use of Ru3(CO)12 as the catalyst and Cu(NO3)2·3H2O as the nitro source, a wide spectrum of arenes bearing diversified N-heterocycles or oximido as the directing groups were nitrated with meta-selectivity exclusively. Mechanism studies have demonstrated the formation of a new 18e-octahedral ruthenium species as a key ortho-CAr-H metalated intermediate, which may be responsible for the subsequent meta-selective electrophilic aromatic substitution (SEAr). Moreover, this approach provides a fast-track strategy for atom/step economical synthesis of many useful pharmaceutical molecules.

3,6-Bis(4-chloro-phen-yl)-N,N-bis-(1-phenyl-eth-yl)-1,2,4,5-tetra-zine-1,4-di-carboxamide.

In the title mol-ecule, C(32)H(28)Cl(2)N(6)O(2), the amide-substituted N atoms of the tetra-zine ring deviate from the approximate plane of the four other atoms in the ring by 0.468 (3) and 0.484 (3) Å, forming a boat conformation. The dihedral angle between the two phenyl rings is 67.0 (1)° and that between the two chloro-substituted benzene rings is 73.8 (1)°. Two intra-molecular N-H⋯N hydrogen bonds are observed.

Manganese(I)-Catalyzed C-H 3,3-Difluoroallylation of Pyridones and Indoles.

A novel and efficient C-H activation approach for the direct 3,3-difluoroallylation of 2-pyridones and indoles is herein reported using a manganese(I) complex as the catalyst. A broad range of substrates with diverse functional groups were tolerated. Moreover, late-stage C-H functionalization of bioactive molecules was achieved in good yield.

Cobalt-Catalyzed Carbonylation of C(sp2)-H Bonds with Azodicarboxylate as the Carbonyl Source.

A novel and efficient approach for the C(sp2)-H bond carbonylation of benzamides has been developed using stable and inexpensive Co(OAc)2·4H2O as the catalyst and the commercially available and easily handling azodicarboxylates as the nontoxic carbonyl source. A broad range of substrates bearing diverse functional groups were tolerated. This is the first example where cobalt-catalyzed C(sp2)-H bond carbonylation occurs with azodicarboxylate as the carbonyl source.