The reactive 16e-species Cp2Ti=CH2 can be generated in situ from either its aluminum alkyl adducts or olefin adducts (metallacyclobutanes). This complex reacts with a wide variety of unsaturated functionalities including :;;c=O, :::c=C~, -c=c-and -C=N. In most instances the ;:c:O groups are methylenated. Key to the utility of these complexes is their lack of basic properties in contrast with phosphorous ylides; all of the normal "Wittig" side reactions are eliminated using these reagents. Acid chlorides and anhydrides are converted into enolate complexes, which can be used in aldol type chemistry. The combination of the reactivity toward C=O and C=C results in an efficient method for the conversion of unhindered carbonyl centers into quarternary carbon centers. BACKGROUNDAlkylidene complexes of high oxidation state transition metals have been recognized for the past several years. They were first proposed as intermediates in numerous reactions (1), and have been isolated recently as tantalum (2), tungsten (3), and titanium (4) complexes. The low valent analogs prepared earlier show different types of reactions and trends in stability (5). The high oxidation state complexes /CH 3

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Significance: Reported is an elegant Cu-catalyzed amidation/hydroamidation of haloenynes with tert-butyl carbamate or bis(Boc)hydrazine affording, after TFA-induced deprotection/tautomerization, highly substituted pyrroles and pyrazoles in good to excellent yields. N,N′-Dimethylethylenediamine (20 mol%) was found to be the most effective ligand for the conversion. Intermediary amidation products were isolated, thus validating the proposed sequence of C-N coupling followed by hydroamidation.Comment: Are copper salts on the verge of a renaissance? Recently, long after the Ullmann reaction, Cu-catalyzed processes have become increasingly competitive with popular Pd catalysis for C-C, C-heteroatom (N, O, P, S, Se) to C-H and C-metal bond forming reactions (see first review below). The current method efficiently extends Cu catalysis by amalgamating well-developed C-N coupling (see second review below) with recent amidation chemistry (L. Ackermann Org. Lett. 2005, 7, 439-442). The scope of this reaction offers highly functionalized disubstituted and trisubstituted pyrroles and pyrazoles bearing alkene, ester, silyl ether, and alkyl halide handles for further potential synthetic manipulation.