Ingo Klement

PREPARATION OF POLYFUNCTIONAL ARYL AND ALKENYL ZINC HALIDES FROM FUNCTIONALIZED UNSATURATED ORGANOLITHIUMS AND THEIR REACTIVITY IN CROSS-COUPLING AND CONJUGATED ADDITION REACTIONS

Abstract Functionalized aryl and alkenyl iodides undergo an iodine-lithium exchange at −90 to −80 °C providing polyfunctional organolithiums which are stable for a short time at these low temperatures and can be transmetalated to organozinc derivatives by the addition of zinc bromide. The resulting unsaturated organozinc halides can then be warmed up and are perfectly stable at 25 °C. They react directly with tosyl cyanide. In the presence of CuCN·2LiCl, they add in a Michael-fashion to alkylidenemalonates. In the presence of catalytic amounts of Pd(dba)2 and TPP or TFP, they undergo readily a cross-coupling at 25 °C with aryl and alkenyl iodides. The Pd-catalyzed coupling of arylzinc bromides with aryl triflates could also be achieved by using dppf as a ligand and 60 °C as reaction temperature.

Preparation of polyfunctional nitriles by the Cyanation of functionalized organozinc halides with p-toluenesulfonyl cyanide

Abstract Various alkyl, alkenyl, akynyl, benzylic, aromatic or heterocyclic organozinc halides bearing functional groups such as an ester, a boronic ester, a cyanide, a halide or a trialkoxysilyl group react under mild conditions with p-toluenesulfonyl cyanide affording polyfunctional nitriles in 69–93 % yields.

Preparation of alkylzinc bromides using a new Mn/Cu catalyzed bromine-zinc exchange reaction

The reaction of functionalized primary alkyl bromides with Et2Zn in DMPU in the presence of a catalytic mixed metal system constituted of MnBr2 (or FeCl3) and CuCl provides functionalyzed alkylzinc bromides (> 80 % yield). In the presence of PdCl2(dppf) or CuCN·2LiCl, these organozinc species reach with a range of electrophiles providing various polyfunctional molecules in good yields.

New mixed metal (Mn/Cu) catalyzed stereoselective cyclizations

Abstract Unsaturated alkyl bromides of type 1 undergo a stereoselective ring closure when treated with a MnBr 2 (5 mol%)/CuCl(3 mol%) catalytic mixed metal system and diethylzinc at 60 °C in DMPU affording five membered carbo- and heterocycles. An alternative Ni-catalyzed cyclization of bromoalkylketones is also described. Remarkably in this case, the iodine-zinc exchange could be performed with EtZnBr instead of pyrophoric Et 2 Zn.

Oxidation of zinc organometallics prepared by hydrozincation or carbozincation using oxygen

Abstract Organozinc compounds prepared by the hydrozincation or carbozincation of functionalized unsaturated molecules can be directly oxidized by oxygen affording alcohols after reductive workup in satisfactory yields.

Chemoselective oxidation of organozinc reagents with oxygen

Abstract Functionalized organozinc compounds prepared by hydrozincation, carbozincation or by boron-zinc exchange can be directly oxidized in a selective manner to the corresponding functionalized alcohols or hydroperoxides depending on the reaction conditions.

Preparation and reactivity of functionalized aryl and alkenylmanganese halides

Abstract Various functionalized aryl and alkenyl manganese halides have been prepared from the corresponding aryl and alkenylhalides according to a one-pot procedure: lithium-halogen exchange at low temperature then LiMn transmetallation.