Intramolecular Hydroamination Of Alkynes Research Articles

Use of Group 4 Bis(sulfonamido) Complexes in the Intramolecular Hydroamination of Alkynes and Allenes.

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Use of group 4 bis(sulfonamido) complexes in the intramolecular hydroamination of alkynes and allenes.

Titanium tetrakis(amido) complexes catalyze the intramolecular hydroamination of alkynes and allenes more efficiently than Cp-based species. We report here that electron-withdrawing and sterically demanding bis(sulfonamido) ligands lead to enhanced catalytic activity. Zirconium analogues have also been prepared, and the tosyl-substituted complex 20 has been structurally characterized. As in the titanium series, bis(sulfonamido) zirconium catalysts are more efficient in the intramolecular hydroamination of allenes than bis(cyclopentadienyl) complex Cp(2)ZrMe(2) (23). Furthermore, these compounds transform 1,3-disubstituted aminoallenes with high stereoselectivity to the Z-allylamines and allow the hydroamination of a trisubstituted allene. Titanium bis(sulfonamido) imido complex 27 was synthesized. It converts aminoallene 10 to cylic imine 11 with a rate comparable to that of tetrakis(amide) 15, supporting the hypothesis of a catalytically active titanium imido intermediate.

Group‐IV Metal Complexes as Hydroamination Catalysts

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Group‐IV Metal Complexes as Hydroamination Catalysts

AbstractDuring the last 50 years, group‐IV metal complexes have been used extensively as catalysts in organic chemistry. However, a new and rapidly growing field for group‐IV metal catalysis evolved in the 1990s when the groups of Bergman, Livinghouse and Doye found that zirconium and titanium complexes catalyze the inter‐ and intramolecular hydroamination of alkynes and allenes. Starting from early results obtained with zirconocene bis(amides), this review deals mostly with hydroamination reactions based on titanium catalysts. In this context, studies directed towards catalyst development are presented as well as applications of corresponding processes for the synthesis of biologically interesting compounds. However, the Microreview covers group‐IV metal complex catalyzed hydroamination reactions of alkynes and allenes that appeared in the literature before July 31, 2002. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Developing Transition-Metal Catalysts for the Intramolecular Hydroamination of Alkynes

Group 7−12 transition-metal complexes serve as effective catalysts for the regioselective intramolecular hydroamination of aminoalkynes having the general formula RC⋮C(CH2)nNH2 (n = 3, R = H, Ph; n = 4, R = H) and of 2-(phenylethynyl)aniline. Primary products are pyrrolidines and piperidines bearing an α-alkylidene functionality and 2-phenylindole, respectively. Isomerization yields the corresponding pyrrolines and 1,2-dehydropiperidines. The catalytic properties of the transition-metal complexes depend on the appropriate choice of ligand, solvent, temperature, and counteranion. Principles for identifying the most active transition-metal catalysts for the hydroamination of alkynes and for optimizing the reaction conditions are developed. The X-ray crystal structure of one catalyst, [PdCl(triphos)](CF3SO3), has been determined.

Intramolecular hydroamination of alkynes catalysed by late transition metals

The cyclisation of 6-aminohex-1-yne to 2-methyl-1,2-dehydropiperidine in the presence of late transition metal catalysts was examined. The highest catalytic activity was observed for [Cu(CH3CN)4]PF6, as well as with Group 12 metal salts. Slightly lower conversions were obtained with the rhodium(I) and palladium(II) complexes [Rh(COD)(DiPAMP)]BF4 and [Pd(Triphos)][BF4]2. Catalysis was also observed with complexes of all group 9 to 12 metals and [Ru3(CO)12]. All catalytically active complexes contain a metal with a d8 or d10 electronic configuration. This observation allows preliminary conclusions about the mechanism to be made.