Gérard Cahiez

Cobalt-Catalyzed Cross-Coupling Reactions

3.1.2. From Vinylic Grignard Reagents 1437 3.1.3. From Aryl Halides and Alkenyl Acetates 1438 3.2. Aryl-Aryl Cross-coupling 1438 3.2.1. From Aromatic Organometallic Reagents 1438 3.2.2. From Two Aromatic Halides 1440 4. Csp2-Csp3 Cross-coupling Reactions 1440 4.1. Alkenylation 1440 4.1.1. From Aliphatic Organometallic Reagents 1440 4.1.2. From Aliphatic Halides 1442 4.2. Arylation 1442 4.2.1. From Aliphatic Halides 1442 4.2.2. From Aromatic Halides 1445 4.3. Allylation of Aromatic Organometallics 1446 5. Alkynylation 1446 5.1. Pioneering Works 1446 5.2. Benzylation of Acetylenic Grignard Reagents 1446 5.3. Alkylation of Acetylenic Grignard Reagents 1447 5.4. Alkenylation of Acetylenic Grignard Reagents 1447 6. Csp3-Csp3 Cross-coupling 1448 6.1. Allylation 1448 6.1.1. Allylation of Aliphatic Organozinc Compounds 1448

Preparation of Highly Functionalized Grignard Reagents by an Iodine–Magnesium Exchange Reaction and its Application in Solid‐Phase Synthesis

At -40°C aryl iodides that contain other functional groups can be selectively converted into Grignard reagents, which react with electrophiles such as benzaldehyde in the usual manner [Eq. (a)]. Aryl bromides and iodides that are immobilized as esters on a Wang resin behave analogously.

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.

Highly chemo- and stereoselective Fe-catalyzed alkenylation of organomanganese reagents☆

Organomanganese chlorides react with alkenyl iodides, bromides and chlorides in the presence of 3% Fe(acac)3. The reaction takes place under very mild conditions (THF-NMP, rt, 1h) to afford the substituted olefin in excellent yields with a high stereo- and chemoselectivity. Thus an unprotected keto alkenyl chloride selectively gives the corresponding keto olefin. From a preparative point of view, this procedure is the first real alternative to the Pd- and Ni-cross coupling reaction used until now.

Cu-catalyzed alkylation and Fe-catalyzed alkenylation of organomanganese reagents

Two new selective C-C bond formation procedures are described; the Cu- catalyzed alkylation of organomanganese chlorides by alkyl halides and the Fe- catalyzed alkenylation of organomanganese chlorides by alkenyl halides. These reactions have a large scope and give high yields under mild conditions (rt, 1 h). They are highly chemoselective and allow the preparation of numerous functionalized molecules. In both cases, the presence of NMP as cosolvent (THFNMP) is determinant. For preparative organic chemistry, these two reactions compare favorably to the other related procedures since they are very easy to carry out and involve no toxic or expensive product. The Fe-catalyzed reaction is the first general Fe-catalyzed alkenylation procedure of preparative interest since no excess of alkenyl halides is required and even alkenyl chlorides can be used successfulIy.

New Polyfunctional Magnesium Reagents for Organic Synthesis

The iodine-magnesium exchange reaction allows the preparation of polyfunctional aryl, heteroaryl, or alkenyl magnesium reagents at low temperature. These reagents display the typical reactivity of Grignard compounds and undergo various copper-catalyzed reactions such as allylation or 1,4-addition. Using this halogen-metal exchange reaction, it was possible to generate polyfunctional magnesium reagents on the solid phase.

Darstellung hochfunktionalisierter Grignard-Reagentien durch eine Iod-Magnesium- Austauschreaktion und ihre Anwendung in der Festphasensynthese

Bei −40 °C lassen sich Aryliodide, die noch weitere funktionelle Gruppen tragen, selektiv in Grignard-Reagentien umwandeln, die dann mit Elektrophilen wie Benzaldehyd wie ublich weiterreagieren [Gl. (a)]. Aryliodide (und -bromide!), die als Ester an einem Wang-Harz immobilisiert sind, reagieren analog.

COBALT-CATALYZED ALKENYLATION OF ORGANOMAGNESIUM REAGENTS

Abstract Alkenyl iodides, bromides and chlorides react with organomagnesium reagents in THF, in the presence of Co(acac)2 and NMP (9 to 4 equiv.), to give the cross-coupling products in good yields. The reaction is chemoselective (aryl or alkyl bromides, esters and ketones) and stereoselective (≥99.5%).

Organomanganese(II) reagents. XV: Conjugate addition of organomanganese reagents to alkylidenemalonic esters and related compounds

Abstract Organomanganese reagents react with alkylidenemalonic esters or related compounds to give the conjugate addition products in good yields. Several examples illustrate the scope and the efficiency of this reaction

A New Efficient Catalytic System for the Chemoselective Cobalt-Catalyzed Cross-Coupling of Aryl Grignard Reagents with Primary and Secondary Alkyl Bromides

The cobalt-catalyzed alkylation of aromatic Grignard reagents is performed in good yields by using a new simple and efficient catalytic system: CoCl(2)/TMEDA (1:1). Primary and secondary cyclic or acyclic alkyl bromides were used successfully. The reaction is highly chemoselective since ester, amide, and keto groups are tolerated. The procedure is inexpensive and very easy to carry out on a larger scale.