The synthesis of functionalized aromatic and heteroaromatic amines has attracted much interest due to their importance as building blocks for pharmaceuticals, polymers, or materials. In this microreview, new developments involving palladium-, nickel-, and copper-catalyzed amination reactions are discussed. The synthesis of functionalized secondary amines or diarylamines by addition of polyfunctionalized arylmagne-

All crossed: The reaction of unsaturated copper reagents with various alkynyl lithium compounds provides mixed lithium cuprates, which in the presence of chloranil undergo an oxidative coupling, thus leading to polyfunctional alkynes or enynes. Bromoenynes prepared by this method are readily converted into pyridine derivatives by a new ring closure that proceeds at low temperature (see scheme, tol=tolyl).

The metalation of arenes and heterocycles is of considerable interest, since it allows direct functionalization of an unactivated CÀH bond by the stoichiometric formation of an organometallic intermediate. Whereas the lithiation of unsaturated organic substrates has been extensively used, [1] the search for metalation procedures that are compatible with more functional groups and proceed at close to room temperature has been the subject of considerable efforts. In this regard, the development of various "ate" bases has been very promising. [2,3] Also, the use of sterically hindered metallic amides complexed by LiCl of the type tmp n M 1 ·x M 2 X m ·y LiCl (tmp = 2,2,6,6-tetramethylpiperidyl; M 1 = Mg, [4] Zn, [5] Al; [6] M 2 = Mg) has led to highly chemoand regioselective metalations. The presence of LiCl was essential since it increases the solubility of these metallic bases and enhances their kinetic basicity by lowering their aggregation states. [7] The preparation of transition-metal amides has been envisioned, as transition metals display reactivity patterns not accessible for main-group elements.[8] Especially manganese, owing to its low price, moderate toxicity, and versatile reactivity, is of synthetic interest.[9] Herein, we report a new manganese base [10] that shows a unique chemoselectivity and reactivity, allowing the efficient formation of CÀC and CÀN bonds. Furthermore, the convenient metalation conditions make it a very practical base for synthetic applications. Thus, the addition of commercially available tmmpMgCl·LiCl (2; 2.0 equiv) to MnCl 2 ·2 LiCl [11] (1 equiv) at 0 8C with subsequent stirring at 25 8C for 3 h provides the manganese amide 3 as a 0.5 m solution in THF (Scheme 1). The base 3 has an excellent thermal stability and can be stored at 25 8C for more than eight weeks without appreciable decomposition. Preliminary experiments show immediately that the new Mn base has a very different reactivity than the Mg base 2. Thus, whereas the reaction of 2 with 2-phenyl-1,3,4-oxadiazole (4) provides only ring fragmentation products (PhCN and NCOMgCl), its metalation with 3 furnishes cleanly the corresponding diheteroaryl manganese reagent, which smoothly adds to benzaldehyde, thus providing the alcohol 5 in 77 % yield (Scheme 1).Remarkably, we found that a range of functionalized aromatic substrates are readily manganated under convenient reaction conditions (0-25 8C). Thus, methyl 4-bromobenzoate (6 a) reacts with 3 (0.6 equiv) within 3.5 h at 25 8C, furnishing the diaryl manganese reagent 7 a without cleavage of the sensitive methyl ester function. Copper(I)-catalyzed acylation using CuCN·2 LiCl [12] (20 mol %) and 2-thienoyl chloride (1.2 equiv) provides the ketone 8 a in 77 % yield. The highly functionalized benzophenone derivative 6 b is converted to the corresponding manganese species 7 b by the reaction with 3 (0.6 equiv, 25 8C, 2 h). Cu I -catalyzed allylation with 3-bromocyclohexene (1.2 equiv) provides the polyfunctional benzophenone 8 b in 74 % yield (Scheme 2).Subsequent palladium...

Dibenzothiophenes, benzo [b]thiophenes, and benzo[c]thiophenes have found numerous applications as dyes, pharmaceuticals, agrochemicals, or as building blocks for the synthesis of conducting polymers. [1,2] Several straightforward strategies for the synthesis of such S heterocycles have been reported.[3] Palladium-catalyzed ring closures leading to S heterocycles are especially difficult, but were realized recently, despite the deactivating effect of sulfur on transition-metal catalysts. [4, 5] To avoid this poisoning of the transition-metal catalysts by thiols and thiolates, we have envisioned a ring-closure procedure involving main-group benzothiolates such as 1 as precursors, which will provide an intermediate such as 2 by an addition/elimination reaction.[6]The elimination of Met-X should result in various dibenzothiophenes of type 3 (Scheme 1).Herein we report the successful synthesis of various classes of S heterocycles of types 3 and 4 [7] as well as[8] and the previously unknown [1]benzothieno [2,3-b][1]benzofuran 6 (Scheme 1), starting from readily available biaryls of type 7. A Br/Mg or I/Mg exchange on the aryl bromides or iodides 8 was first carried out with iPrMgCl·LiCl [9] (À20 8C, 0.5-2 h) and then transmetalated with ZnCl 2 . A subsequent Negishi cross-coupling reaction [10][11][12] ([Pd(dba) 2 ] (2 mol %; dba = trans,trans-dibenzylideneacetone), tri-2-furylphosphine (tfp; 4 mol %, 50 8C, 1.5 h)) with functionalized 1-chloro-2-iodobenzene derivatives 9 then afforded the polysubstituted biphenyls 10 in 75-92 % yield. Br/Li exchange proved to be superior (nBuLi (1.1 equiv), À95 8C, 30 min) as these biphenyls did not undergo complete Br/Mg exchange because of steric hindrance. After transmetalation with the THF-soluble magnesium complex MgCl 2 ·LiCl, [13,14] the resulting aryl magnesium species were treated with tetramethylthiuram disulfide (Me 2 NC(S)S) 2 (0.9 equiv, 0 8C to 258C, 1 h) [15] to provide the biphenyl dithiocarbamates 7 a-f in yields of 80-94 % (Scheme 2).This synthesis was also extended to the preparation of benzothiophenes 11 a-d and benzofurans 12 a/b. Thus, 3-bromobenzothiophene (13 a) was magnesiated with iPrMgCl·LiCl [9] (1.1 equiv, À15 8C, 24 h) to the corresponding magnesium derivative. Subsequent transmetalation with ZnCl 2 and a Negishi cross-coupling reaction [10][11][12] with 1-bromo-2-iodobenzene derivatives 14 ([Pd(dba) 2 ] (2 mol %), tfp (4 mol %), 50 8C, 1.5 h) then resulted in the formation of the 3-arylated benzothiophenes 15 a-d (63-75 % yield; Scheme 1. Preparation of S heterocycles by an addition/elimination reaction. FG = functional group, Met = K, X = Br, Cl.Scheme 2. Preparation of the starting dithiocarbamates 7.

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