Cobalt-Catalyzed Cross-Couplings of Bench-Stable Alkynylzinc Pivalates with (Hetero)Aryl and Alkenyl Halides.

A catalytic system consisting of CoCl2·2LiCl and TMEDA enables the cross-coupling of various electron-poor aryl and heteroaryl halides with various alkynylzinc pivalates. Coupling with alkenyl halides proceeds with retention of configuration.

Pore geometry effect on the synthesis of silica supported perovskite oxides.

The formation of perovskite oxide nanoparticles supported on ordered mesoporous silica with different pore geometry is here presented. Systematic study was performed varying both pore shape (gyroidal, cylindrical, spherical) and size (7.5, 12, 17nm) of the hosts. LaFeO3, PrFeO3 and LaCoO3 were chosen as target guest structures. The distribution of the oxide nanoparticles on silica was comprehensively assessed using a multi-technique approach. It could be shown that the pore geometry plays a determining role in the conversion of the infiltrated metal nitrates to metal oxide. In particular, slow degradation kinetic was observed in highly curved pores, which fostered nucleation and crystallization of the guest species. In spherical pore systems the enhancement of pore size caused a remarkable delay of the decomposition of the metal salts, but at the same time improved the homogeneous distribution of the oxide particles in the matrix.

A Robust and Broadly Applicable Cobalt-Catalyzed Cross-Coupling of Functionalized Bench-Stable Organozinc Pivalates with Unsaturated Halides.

We report a robust and broadly applicable CoCl2 -catalyzed cross-coupling between functionalized aryl and heteroaryl zinc pivalates and various electron-poor aryl and heteroaryl halides (X=Cl, Br, I). Couplings with (E)- or (Z)-bromo- or iodo-alkenes proceed with retention of configuration. Also, alkynyl bromides react with arylzinc pivalates providing arylated alkynes.

Directed Zincation with TMPZnCl·LiCl and Further Functionalization of the Tropolone Scaffold.

The directed zincation of tropolone derivatives was achieved using TMPZnCl·LiCl. Various functionalizations of the zincated intermediates by halogenation, acylation, allylation, and Negishi cross-coupling were successfully performed. Additionally, 1,8-conjugate addition-elimination reactions with a variety of arylmagnesium and secondary alkylzinc reagents were carried out to further elaborate the tropolone core.

Cobalt-Catalyzed C(sp2)-C(sp3) Cross-Coupling Reactions of Diarylmanganese Reagents with Secondary Alkyl Iodides.

A cobalt-catalyzed cross-coupling of diarylmanganese reagents with secondary alkyl iodides using the THF-soluble salt CoCl2·2LiCl, which leads to the cross-coupling products in up to 92% yield, is reported. High diastereoselectivities can be reached in these cross-couplings (dr up to 99:1). Remarkably, rearrangement of secondary alkyl iodides to unbranched products was not observed in these C-C forming reactions.

Diastereoselective Cobalt-Mediated Cross-Couplings of Cycloalkyl Iodides with Alkynyl or (Hetero)Aryl Grignard Reagents.

A highly diastereoselective cross-coupling of variously substituted cycloalkyl iodides with alkynyl and (hetero)aryl Grignard reagents using cobalt(II) chloride has been successfully developed. With the THF-soluble CoCl2·LiCl and the inexpensive ortho-phenanthroline derivative, neocuproine, as a ligand, diastereomeric ratios of up to 99:1 were achieved. A range of functional groups are tolerated in the Grignard reagent (e.g., CF3, Piv, CN, OPiv, NMe2, CO2NEt2, SF5, OTBS).

Mild Cobalt-Catalyzed Negishi Cross-Couplings of (Hetero)arylzinc Reagents with (Hetero)aryl Halides.

A catalytic system consisting of CoCl2 ⋅2 LiCl (5 mol %) and HCO2 Na (50 mol %) enables the cross-coupling of various N-heterocyclic chlorides and bromides as well as aromatic halogenated ketones with various electron-rich and -poor arylzinc reagents. The reactions reached full conversion within a few hours at 25 °C.

Zincation of 4,4-dimethyloxazoline using TMPZnCl·LiCl. A new preparation of 2-aryloxazolines.

The metalation of 4,4-dimethyloxazoline using TMPZnCl·LiCl provides a stable 2-zincated oxazolinyl reagent which readily undergoes palladium-catalyzed Negishi cross-couplings allowing a new access to 2-aryloxazolines. Cu-mediated acylation and allylation reactions also proceed in good yields.

Cobalt-catalyzed negishi cross-coupling reactions of (hetero)arylzinc reagents with primary and secondary alkyl bromides and iodides.

We report a cobalt-catalyzed cross-coupling of di(hetero)arylzinc reagents with primary and secondary alkyl iodides or bromides using THF-soluble CoCl2 ⋅2 LiCl and TMEDA as a ligand, which leads to the corresponding alkylated products in up to 88 % yield. A range of functional groups (e.g. COOR, CN, CF3 , F) are tolerated in these substitution reactions. Remarkably, we do not observe rearrangement of secondary alkyl iodides to unbranched products. Additionally, the use of cyclic TBS-protected iodohydrins leads to trans-2-arylcyclohexanol derivatives in excellent diastereoselectivities (up to d.r.=99:1).

Regioselective functionalization of the oxazole scaffold using TMP-bases of Mg and Zn.

A general method for the synthesis of 2,4,5-trisubstituted oxazoles has been developed. Starting from commercially available oxazole, successive metalations using TMPMgCl·LiCl or TMPZnCl·LiCl led to the corresponding magnesiated or zincated species which were stable toward ring fragmentation. Furthermore, they readily reacted with various electrophiles, such as aryl and allylic halides, acid chlorides, TMSCl, and TMS-CN, providing highly functionalized oxazoles.

Direct Pd-catalyzed cross-coupling of functionalized organoaluminum reagents.

A handsome couple: Through the use of the simple Pd catalyst [Pd(tmpp)(2)Cl(2)] (tmpp = tris(2,4,6-trimethoxyphenyl)phosphine) and THF/DMF as solvent, various aryl-, heteroaryl-, benzyl- and alkylaluminum reagents can be readily cross-coupled with aryl or heteroaryl iodides, bromides, and nonaflates, and in special cases even with chlorides and triflates. This cross-coupling tolerates free NH(2) groups, aldehydes, ketones, esters, and nitro functions.