A convenient alumination of functionalized aromatics by using the frustrated Lewis pair Et3 Al and TMPMgCl⋅LiCl.

A straightforward and efficient alumination of functionalized arenes by using the frustrated Lewis pair Et3 Al and TMPMgCl⋅LiCl (TMP=2,2,6,6-tetramethylpiperidyl) has been developed. In particular, halogenated electron-rich aromatics can be smoothly functionalized by using the frustrated Lewis pair Et3 Al and TMPMgCl⋅LiCl. Compared with previously described alumination methods, this procedure avoids extensive cooling and the need for an excess of base.

New preparation of TMPZnCl·LiCl by Zn insertion into TMPCl. Application to the functionalization of dibromodiazines.

A practical zinc insertion starting from cheap commercial zinc powder and TMPCl (1-chloro-2,2,6,6-tetramethylpiperidine) allows a fast and efficient synthesis of the zinc base TMPZnCl·LiCl under mild conditions in high yields. This base is kinetically highly active and was used for the regio- and chemoselective functionalization of dibromodiazines (pyridazines and pyrazines).

Stereoselective synthesis of tetrasubstituted alkenes via a sequential carbocupration and a new sulfur-lithium exchange.

We have designed a new sequential carbocupration and sulfur-lithium exchange that leads stereo- and regioselectively to trisubstituted alkenyllithiums. Subsequent trapping with various electrophiles yields tetrasubstituted olefins with good control of the double-bond geometry (E/Z ratio up to 99:1). The novel sulfur-lithium exchange could be extended to the stereoselective preparation of Z-styryl lithium derivatives with almost complete retention of the double-bond geometry.

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.

Regioselective zincation of indazoles using TMP2Zn and Negishi cross-coupling with aryl and heteroaryl iodides.

The metalation of various SEM-protected functionalized indazoles with TMP(2)Zn provides 3-zincated indazoles which undergo palladium-catalyzed Negishi cross-couplings in good yields.

Direct zincation of functionalized aromatics and heterocycles by using a magnesium base in the presence of ZnCl2.

A wide range of polyfunctional aryl and heteroaryl zinc reagents were efficiently prepared in THF by using (TMP)(2)Mg2 LiCl (TMP=2,2,6,6-tetramethylpiperamidyl) in the presence of ZnCl(2). The possible pathways of this metalation procedure as well as possible reactive intermediates are discussed. This experimental protocol expands the tolerance of functional groups and allows an efficient zincation of sensitive heterocycles such as quinoxaline or pyrazine.