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Relevant academic research and scientific papers

DIKETIMINATO CU(I) AND CO(I) CARBENE CATALYSTS, AND CYCLOPROPANATION METHODS USING THEM

The present invention described herein employs employs Cu(I) complexes of an electron-rich, bidentate N,N-donor ligand (P-diketiminates) that react with both heteroatomcontaining a-substituted diazomethanes and ary1diazomethanes to yield a unique metal-carbene complex stabilized by two metal fragments that selectively reacts with alkenes. These examples are the first of isolable Cu-carbene complexes that react with alkenes to give cyclopropanes. Furthermore, electron-rich, bidentate N,N-donor ligands can be designed to impart stereo- and enantio-selectivity in the cyclopropanation of alkenes with diazoalkanes.

Discrete bridging and terminal copper carbenes in copper-catalyzed cyclopropanation

The Cu(I)/ β-diketiminate [Me2NN]Cu(η2- ethylene) (2) catalyzes the cyclopropanation of styrene with N 2CPh2 to give 1,1,2-triphenylcyclopropane in 67% yield. Addition of N2CPh2 to 2 equiv of 2 allows for the isolation of the dicopper carbene {[Me2NN]Cu}2(μ- CPh2) (3) in which the diphenylcarbene moiety is symmetrically bound between two [Me2NN]Cu fragments (Cu-C = 1,922(4) and 1.930(4) A) with a Cu-Cu separation of 2.4635(7) A. In toluene-d8 solution, 3 reversibly dissociates a [Me2NN]Cu fragment to give [Me2NN]Cu(toluene) and the terminal carbene [Me2NN]Cu= CPh2, Dicopper carbene 3 reacts with 3 equiv of styrene to give 1,1,2-triphenylcyclopropane and 2 equiv of [Me2NN] Cu(η2-styrene) within minutes, DFT studies with simplified ligands indicate a stronger Cu-C π-back-bonding interaction from two Cu(I) centers to the carbene acceptor orbital in a dicopper carbene than that present in a monocopper carbene. Nonetheless, the terminal carbene [Me 3NN]Cu=CPh2 (8) that possesses a p-methyl group on each β-diketiminato N-aryl ring may be isolated and exhibits a shortened Cu-C distance of 1,834(3) A, The stoichiometric cyclopropanation of styrene by 8 in 1,4-dioxane is first-order in both copper carbene 8 and styrene with activation parameters ΔH? = 10,4(3) kcal/mol and ΔS? = -32,3(9) cal/mol·K. In 1,4-dioxane, 8 decomposes to Ph 2C=CPh2 via first-order kinetics with activation parameters ΔH? = 21(1) kcal/mol and ΔS? = -8(3) cal/mol·K. Arene solutions of thermally sensitive terminal carbene 8 decompose to [Me3NN]-Cu(arene), which reacts with 8 still present in solution to give the more thermally stable {[Me3NN]Cu} 2-(μ-CPh2).

Photolysis of 1,1,1-Triarylalk-2-enes and 1,1,1-Triarylhept-2-ynes. A Novel Generation of Aryl(alk-1-enyl)carbenes ans Aryl(alk-1-ynyl)carbenes

Upon UV irradiation in methanol, 1,1,1-triarylhept-2-ynes underwent an α,α-elimination of two aryl groups to give a biaryl and the corresponding carbene which reacted with methanol to give a 1-aryl-1-methoxyhept-2-yne. 1,1,1-Triphenylalk-2-enes underwent α,α-elimination of two phenyl groups and also elimination of an alkene and a phenyl group to give biphenyl and a 1-phenylalkene respectively.In both cases, the corresponding carbenes were formed and were isolated as methanol insertion products (a 1-methoxy-1-phenylalk-2-ene and diphenylmethyl methyl ether, respectively).A rearrangement product, a 1,1,2-triphenylcyclopropane, was also formed.

Photolysis of 1,1,1-Triphenyl-2-alkenes and Methyl Triphenylacetate

Upon UV irradiation in methanol 1,1,1-triphenyl-2-alkene or methyl triphenylacetate underwent two kinds of α,α-elimination of two phenyl groups and phenyl-alkenyl groups or phenyl-methoxycarbonyl groups to give biphenyl, 1-phenylalkene or methyl benzoate, and two kinds of correspondending carbene intermediates, which inserted into the O-H bond of methanol to afford two kinds of methyl ethers, respectively.