A new method in which a series of substituted carbazoles is efficiently produced by the combination of an amide and an arene is described. The key feature of this method is the palladium-catalyzed tandem directed C-H functionalization and amide arylation. The method tolerates substitution on either ring of the biaryl amide substrates, and the products can be assembled in a simple two-step protocol from readily available reagents. The Pd(0) species generated are reoxidized to Pd(II) in the presence of Cu(OAc)2 and an atmosphere of oxygen.

The development of a new method for the assembly of unsymmetrical carbazoles is reported. The strategy involves the selective intramolecular functionalization of an arene C-H bond and the formation of a new arene C-N bond. The substitution pattern of the carbazole product can be controlled by the design of the biaryl amide substrate, and the method is compatible with a variety of functional groups. The utility of the new protocol was demonstrated by the concise synthesis of three natural products from commercially available materials.

Two complexes that contain the racemic or enantiomerically pure (S) form of the 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diolate (Biphen(2-)) ligand, W(NAr)(CHCMe(2)Ph)(Biphen) (2a) and W(NAr')(CHCMe(2)Ph)(Biphen) (2b) (Ar = 2,6-i-Pr(2)C(6)H(3); Ar' = 2,6-Me(2)C(6)H(3)), were prepared and shown to be viable catalysts for several representative ring-closing reactions to give products in good yields in most cases and high % ee in asymmetric reactions. Exploration of the reaction between 2a and a stoichiometric amount of one desymmetrization substrate allowed two intermediate tungstacyclobutane complexes to be observed, in addition to the final and quite stable tungstacyclobutane complex formed in a reaction between the ring-closed product and a tungsten methylene complex. Reactions involving (13)C labeled ethylene allowed for the observation of an unsubstituted tungstacyclobutane complex, an ethylene complex, an unsubstituted tungstacyclopentane complex, and a heterochiral dimeric form of a methylene complex. The tungstacyclopentane complex was found to catalyze the dimerization of ethylene to 1-butene slowly.

In this paper we explore reactions between 13 CH 2 d 13 CH 2 and the imido alkylidene complexes, Mo(NArand Mo(NAr Cl )(CHCMe 2 -Ph)[(R)-Benz 2 Bitet] (3e). (See text for a description of Biphen and Benz 2 Bitet.) Under a variety of conditions and for various combinations of imido, alkylidene, and diolate ligands, we have observed R-substituted molybdacyclobutanes Mo(NR)(*CH 2 *CH 2 CHCMe 2 Ph)[diolate] (*C ) 13 C), unsubstituted molybdacyclobutanes Mo(NR)(*CH 2 *CH 2 *CH 2 )[diolate], olefin complexes Mo(NR)(*CH 2 dCHR)[diolate] (R ) H or CMe 2 Ph), molybdacyclopentane complexes Mo(NR)-(*CH 2 *CH 2 *CH 2 *CH 2 )[diolate], and base-free methylene complexes Mo(NR)(*CH 2 )[diolate].We also have crystallographically characterized a molybdenum ethylene complex derived from a biphenolate complex, Mo(N-2,6-Cl 2 C 6 H 3 )(CH 2 dCH 2 )[rac-Biphen](Et 2 O).