Copper Alkynyl Research Articles

Mechanochromic photoluminescence in a dinuclear alkynyl copper(i) complex with an extremely short Cu(i)⋯Cu(i) separation

Mechanochromic phosphorescence of a rare copper(i) dinuclear complex with an extremely short Cu(i)⋯Cu(i) separation.

Asymmetric Substitution by Alkynyl Copper Driven Dearomatization and Rearomatization.

Catalytic asymmetric transformations by dearomatization have developed into a widely applicable synthetic strategy, but heavily relied on the use of arenes bearing a heteroatom. In this case, the dearomatization is facilitated by the involvement of a p-orbital electron of the heteroatom. Different from the conventional substrate-dependent model, here we demonstrate that the activation by a d-orbital electron of the transition-metal center can serve as a driving force for dearomatization, and is applied to the development of a novel asymmetric alkynyl copper facilitated remote substitution reaction. A newly modified PyBox chiral ligand enables the construction of valuable diarylmethyl and triarylmethyl skeletons in high enantioselectivities. An unexpected tandem process involving sequential remote substitution/cyclization/1,5-H shift leads to the formation of the enantioenriched C-N axis. A gram-scale reaction and various downstream transformations highlight the robustness of this method and the potential transformations of the products. Preliminary mechanistic studies reveal a mononuclear Cu-catalyzed remote substitution process.

Asymmetric Substitution by Alkynyl Copper Driven Dearomatization and Rearomatization

AbstractCatalytic asymmetric transformations by dearomatization have developed into a widely applicable synthetic strategy, but heavily relied on the use of arenes bearing a heteroatom. In this case, the dearomatization is facilitated by the involvement of a p‐orbital electron of the heteroatom. Different from the conventional substrate‐dependent model, here we demonstrate that the activation by a d‐orbital electron of the transition‐metal center can serve as a driving force for dearomatization, and is applied to the development of a novel asymmetric alkynyl copper facilitated remote substitution reaction. A newly modified PyBox chiral ligand enables the construction of valuable diarylmethyl and triarylmethyl skeletons in high enantioselectivities. An unexpected tandem process involving sequential remote substitution/cyclization/1,5‐H shift leads to the formation of the enantioenriched C−N axis. A gram‐scale reaction and various downstream transformations highlight the robustness of this method and the potential transformations of the products. Preliminary mechanistic studies reveal a mononuclear Cu‐catalyzed remote substitution process.

Photoinduced Copper-Catalyzed Monofluoroalkylation of Terminal Alkynes to Propargylic Fluorides.

A photoinduced copper-catalyzed strategy for the monofluoroalkylation of alkynes with readily available monofluoroalkyl triflates was developed. It provides a new protocol to access valuable propargyl fluoride compounds via C-C bond formation by avoiding the use of highly toxic fluorination reagents. This reaction proceeded under mild conditions to afford propargyl monofluorides in moderate to high yields. Preliminary mechanistic studies reveal that a ligand-matched alkynyl copper complex might be the key photoactive substance.

Regioselective Alkynylation of Allylic Phosphates with Alkynyl Copper Reagents

AbstractWe developed an alkynylation of allylic phosphates with acetylenes in the presence of copper and magnesium salts. The reaction proceeded regioselectively to afford the corresponding 1,4‐enynes. Furthermore, the functional group tolerance of this reaction was established. As an application, the 1,4‐enyne intermediate involved in the synthesis of 13R,19S,20S‐trihydroxydocosapentaenoic acid could be efficiently synthesized.

CuI -Mediated Bromoalkynylation and Hydroalkynylation Reactions of Unsymmetrical Benzynes: Complementary Modes of Addition.

Benzynes formed by heating a suitable triyne (or tetrayne) substrate are shown to react with in situ generated alkynyl copper species. The latter are compatible with the polyyne substrates and two types of chemistries have been achieved: (i) 1-bromo-1-alkynes efficiently undergo net bromoalkynylation of the (unsymmetrical) benzynes and (ii) in situ generated alkynylcopper species give rise to hydroalkynylation products. The regiochemical preferences of these two modes of reaction are complementary to one another with respect to the position of alkynyl substituent in the final products.

Trifluoromethyl- and Fluoroalkylselenolations of Alkynyl Copper(I) Compounds.

The successful perfluoroalkylselenolation of alkynyl copper(I) compounds is described herein. The reaction occurs under oxidant free conditions at room temperature. This convenient one-pot procedure is based on the in situ generation of trifluoromethylselenyl chlorides. The developed system shows high functional group tolerance and also promotes the employment of fluoroalkyl derivatives.

ChemInform Abstract: SN2‐Selective Allylic Substitution of Chiral γ‐Aryl Substituted Allylic Picolinates with Alkynylcopper Reagents.

Abstract Substitution of γ-aryl secondary allylic picolinates with alkynyl copper reagents was studied. The copper reagent, prepared from TMSC CMgBr and CuBr·Me2S in 2:1, was subjected to substitution of the picolinate derived from (E)-3-phenyl-1-methyl-2-propenyl alcohol at 0 °C for 1 h in THF to produce a mixture of α- and γ-products and the alcohol in 67:20:13, while the reagent in 3 or 4:1 ratio gave the α-product with 90–91% selectivity. On the contrary, reaction in CH2Cl2–THF (6–8:1) at 0 °C for 1 h furnished the α-product with 99% regioselectivity. The effect of CH2Cl2 was also demonstrated with eight more examples. Furthermore, 99% inversion was determined by transformation to the literature compound and by chiral HPLC.

S N2-Selective allylic substitution of chiral γ-aryl substituted allylic picolinates with alkynylcopper reagents

Substitution of γ-aryl secondary allylic picolinates with alkynyl copper reagents was studied. The copper reagent, prepared from TMSC CMgBr and CuBr·Me 2S in 2:1, was subjected to substitution of the picolinate derived from ( E)-3-phenyl-1-methyl-2-propenyl alcohol at 0 °C for 1 h in THF to produce a mixture of α- and γ-products and the alcohol in 67:20:13, while the reagent in 3 or 4:1 ratio gave the α-product with 90–91% selectivity. On the contrary, reaction in CH 2Cl 2–THF (6–8:1) at 0 °C for 1 h furnished the α-product with 99% regioselectivity. The effect of CH 2Cl 2 was also demonstrated with eight more examples. Furthermore, 99% inversion was determined by transformation to the literature compound and by chiral HPLC.

Formation of Chiral C(sp3)−C(sp) Bond by Allylic Substitution of Secondary Allylic Picolinates and Alkynyl Copper Reagents

To establish allylic substitution of secondary allylic alcohol derivatives with alkynyl copper reagents, allylic esters bearing the (2-pyridine)CO2-, (2-pyrazine)CO2-, (EtO)2PO2-, C6F5CO2-, o-(Ph2P)C6H4CO2-, MeOCO2-, or AcO- group were examined. First, picolinate (R1 = Me, R2 = CH2OPMB) was subjected to reaction with (TMS-C[triple bond]C)2CuLi.LiBr at 0degreesC. Although no substitution took place, MgBr2 (3 equiv) was found to promote the reaction to produce the anti SN2' product in 93% yield with 94% regioselectivity and 99% chirality transfer. In contrast, substitution of the other esters with the copper reagent in the presence of MgBr2 were less reactive ((2-pyrazine)CO2-) or marginally reactive (other cases). Generality of the substitution using picolinates was established with five picolinates (R1 = Me, Ph(CH2)2, PMBO(CH2)3; R2 = Me, CH2OPMB, CH2OTBS, C5H11, c-C6H11) and seven alkynyl copper reagents (R3 = TMS, Ph, p-TBSOC6H4, p- and o-MeOC6H4, p-MeC6H4, p-FC6H4), furnishing anti SN2' products in 61-93% yields with high regioselectivity (usually >90%) and high chirality transfer (usually >95%). In addition, transformation of the products was briefly studied.

Enhanced Reactivity of Dinuclear Copper(I) Acetylides in Dipolar Cycloadditions

Dinuclear alkynyl copper(I) complexes exhibit superior reactivity toward organic azides compared to their monomeric analogues. DFT studies indicate that the second copper center facilitates the formation of the cupracycle in the rate-determining step and stabilizes the metallacycle intermediate itself. These findings support the experimentally determined rate law and shed light on the origin of high reactivity of the in situ generated copper acetylides.

Manganese Trifluoroacetoxycarbene Complexes Are Convenient Intermediates in the Synthesis of Cyclic Enediynes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Coupling of 3,8‐Dibromo‐1,10‐phenanthroline with 3,5‐Diethynylheptyloxybenzene: A Suzuki/Miyaura versus a Sonogashira Perspective.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Manganese Trifluoroacetoxycarbene Complexes Are Convenient Intermediates in the Synthesis of Cyclic Enediynes

Trifluoroacetoxycarbene complexes generated from reaction of stable manganese acyl complexes with trifluoroacetic anhydride are convenient alternatives to thermally sensitive manganese carbyne complexes in reactions with diynes that lead eventually to free cyclic enediynes. In situ reaction of these trifluoroacetoxycarbene complexes with alkynyl copper intermediates generated from diynes, CuBr, and NEt(i-Pr)2 led to the isolation of cyclic enediynes via intermediate linked alkynylcarbene complexes and manganese enediyne complexes.

Coupling of 3,8-Dibromo-1,10-phenanthroline with 3,5-Diethynylheptyloxybenzene: A Suzuki/Miyaura Versus a Sonogashira Perspective

We report a new application of the Suzuki-Miyaura reaction whereas two bifunctional reactants, 3,8-dibromo-1,10-phenanthroline and 3,5-diethynylheptyloxylbenzene (9), yield 3,8-bis(3-ethynyl-5-heptyloxyphenylethynyl)-1,10-phenanthroline (2) efficiently (74% yield) without polymerization. This was achieved by reacting a stoichiometric amount of 9 and (Me3Si)2NLi to obtain quantitatively the monoacetylide anion of 9 (10). The latter was activated with B-methoxy-9-BBN and reacted in analogy to the alkynyl copper complex of a Sonogashira route. However, in the Sonogashira reaction, the alkynyl copper complex is present in small equilibrium concentrations and polymerization takes place even when reagents are mixed slowly. Actually the Sonogashira route gave no desired product 2, as the latter polymerizes easily via homo-coupling in the presence of air and Cu(I).

The first conjugate addition reaction of terminal alkynes catalytic in copper: conjugate addition of alkynes in water.

We document that alkynyl copper reagents generated under aqueous conditions from terminal acetylenes, catalytic Cu(OAc)2, and sodium ascorbate undergo additions to Meldrum's acid-derived Michael acceptors at room temperature (Scheme 1). The additions are not only novel, but also constitute the first example of the conjugate addition reaction of an acetylide catalytic in copper.

Transmetalation of palladium enolate and its application in palladium-catalyzed homocoupling of alkynes: a room-temperature, highly efficient route to make diynes.

A novel pathway for the homocoupling reaction has been achieved using a similar protocol as the cross-coupling reaction. Ethyl bromoacetate is chosen to initiate the coupling reaction through oxidative addition to a Pd(0) species, and an PdBr(enolate) intermediate is formed. This intermediate can undergo double transmetalation with an alkynyl copper reagent, and reductive elimination produces a variety of diynes in high yields.

Alkynyl and butadiynyl complexes of the cycloheptatrienylmolybdenum auxiliary Mo(CO) 2(η-C 7H 7)

The new alkynyl complexes [Mo(CCR)(CO) 2(η-C 7H 7)] ( 1, R=Bu t ; 2, R=SiMe 3; 3, R=CO 2Et) have been prepared by reaction of [MoBr(CO) 2(η-C 7H 7)] with alkynyl lithium ( 1, 2) or alkynyl copper ( 3) reagents. The σ-butadienyl complex [Mo{C(C(CN) 2)C(Ph)C(CN) 2}(CO) 2(η-C 7H 7)] 6, is formed by reaction of [Mo(CCPh)(CO) 2(η-C 7H 7)] with tetracyanoethene. Treatment of [MoBr(CO) 2(η-C 7H 7)] with LiCCCCSiMe 3 affords [Mo(CCCCSiMe 3)(CO) 2(η-C 7H 7)] 7 which is a precursor to [Mo(CCCCH)(CO) 2(η-C 7H 7)] 8 by desilylation with KF in methanol/THF. The butadiynyl complexes [Mo(CCCCH)(CO)L(η-C 7H 7)] ( 8, L=CO; 9, L=PMe 3) are also formed directly by reaction of [MoBr(CO)L(η-C 7H 7)] with Li 2CCCC in THF.