Theoretical Investigation into the Mechanism of Au(I)-Catalyzed Reaction of Alcohols with 1,5 Enynes

Enantioselective gold(i)-catalyzed cyclization/intermolecular nucleophilic additions of 1,5-enyne derivatives

An enantioselective Au(i)-catalyzed cyclization/nucleophilic addition process is developed, starting from 1,5-enyne substrates. A broad scope of O-, N- and C-nucleophiles was introduced in order to provide the corresponding chiral cyclopentene derivatives in moderate to high yields and up to 96 : 4 enantiomeric ratio.

Computational study on the 1,3-diyne synthesis from gold(i)-catalyzed alkynylation of terminal alkynes with alkynyl hypervalent iodine reagents under the aid of a silver complex and 1,10-phenanthroline

DFT calculations reveal a new Au/Ag co-catalyzed π-activation mechanism for the formation of unsymmetrical 1,3-diyne.

Gold(i)-catalyzed nucleophilic cyclization of β-monosubstituted o-(alkynyl)styrenes: a combined experimental and computational study

The diastereospecific 5-endo cyclization of β-monosubstituted o-(alkynyl)styrenes to 1-functionalized-1H-indenes is reported. The regiospecific generation of a cyclopropyl gold carbene intermediate is also supported by DFT calculations.

Synthesis of substituted 4-hydroxyalkyl-quinoline derivatives by a three-component reaction using CuCl/AuCl as sequential catalysts

A new method to construct 4-hydroxyalkyl-quinoline derivatives is described via Cu(i) and Au(i) sequential catalyzed cyclization of anilines with aldehyde derivatives and aliphatic alkynes, respectively.

Theoretical insight into the zinc(ii)-catalyzed synthesis of 2-indolyltetrahydroquinolines from N-propargylanilines and indoles: cross-dehydrogenative coupling with temporally separated catalytic activity

An abnormal catalytic cascade reaction with temporally separated catalytic activity.

Unveiling Secrets of Overcoming the "Heteroatom Problem" in Palladium-Catalyzed Aerobic C-H Functionalization of Heterocycles: A DFT Mechanistic Study

Directed C-H functionalization of heterocycles through an exocyclic directing group (DG) is challenging due to the interference of the endocyclic heteroatom(s). Recently, the "heteroatom problem" was circumvented with the development of the protection-free Pd-catalyzed aerobic C-H functionalization of heterocycles guided by an exocyclic CONHOMe DG. We herein provide DFT mechanistic insights to facilitate the expansion of the strategy. The transformation proceeds as follows. First, the Pd2(dba)3 precursor interacts with t-BuNC (L, one of the substrates) and O2 to form the L2Pd(II)-η(2)-O2 peroxopalladium(II) species that can selectively oxidize N-methoxy amide (e.g., PyCONHOMe) substrate, giving an active L2Pd(II)X2 (X = PyCONOMe) species and releasing H2O2. After t-BuNC ligand migratory insertion followed by a 1,3-acyl migration and association with another t-BuNC, L2Pd(II)X2 converts to a more stable C-amidinyl L2Pd(II)XX' (X' = PyCON(t-Bu)C═NOMe) species. Finally, L2Pd(II)XX' undergoes C-H activation and C-C reductive elimination, affording the product. The C-H activation is the rate-determining step. The success of the strategy has three origins: (i) the N-methoxy amide DG can be easily oxidized in situ to generate the active L2Pd(II)X2 species via the oxidase pathway, thus preventing the destructive oxygenase pathway leading to stable t-BuNCO or the O-bridged dimeric Pd(II) species. The methoxy group in this amide DG greatly facilitates the oxidase pathway, and the tautomerization of N-methoxy amide to its imidic acid tautomer makes the oxidation of the substrate even easier. (ii) The X group in L2Pd(II)X2 can serve as an internal base to promote the C-H activation via CMD (concerted metalation-deprotonation) mechanism. (iii) The strong coordination ability of t-BuNC substrate/ligand suppresses the conventional cyclopalladation pathway enabled by the coordination of an endocyclic heteroatom to the Pd-center.

Ligand-controlled gold-catalyzed cycloisomerization of 1,n-enyne esters toward synthesis of dihydronaphthalene

We describe herein a gold-catalyzed rearrangement of propargyl esters followed by allene–ene cyclization to afford substituted bicyclic [4.4.0] dihydronaphthalene compounds.

Triazole-gold promoted intermolecular propargyl alcohol addition to alkyne: the reaction cascade toward substituted allenes

Gold-catalyzed intermolecular propargyl alcohol addition to alkyne was achieved. The reaction of propargyl alcohol with a typical gold catalyst gave the hydration product almost exclusively. The triazole gold catalyst (TA-Au) successfully prevented the hydration, giving the vinyl ether followed by a 3,3-rearrangement. Synthetically useful substituted allenes were formed with high efficiency, substrate tolerability and chemoselectivity. Also, more than 95% chirality transfer from propargyl alcohol to allene was obtained.

Noninnocent counterion effect on the rearrangements of cationic intermediates in a gold(I)-catalyzed alkenylsilylation reaction

A mechanistic DFT study of the gold(I)-catalyzed alkenylsilylation reaction of a silyl-tethered 1,6-enyne system is reported. A novel pathway involving bistriflimide counterion-assisted rearrangements of carbocation and silyl cation intermediates corroborates the experimental observations. The results suggest the important role of the counterion in modulating the reactivity of cationic intermediates in gold catalysis.