Palladium- and base-free synthesis of conjugated ynones by cross-coupling reactions of alkynylboronates with acid chlorides mediated by CuCl

trans-Hydroalkynylation of Internal 1,3-Enynes Enabled by Cooperative Catalysis

A cooperative catalyst system involving a Pd(0)/Senphos complex, tris(pentafluorophenyl)borane, copper bromide, and an amine base, is demonstrated to catalyze trans-hydroalkynylation of internal 1,3-enynes. For the first time, a Lewis acid catalyst is shown to promote the reaction involving the emerging outer-sphere oxidative reaction step. The resulting cross-conjugated dieneynes are versatile synthons for organic synthesis, and their characterization reveals distinct photophysical properties depending on the positioning of the donor/acceptor substituents along the conjugation path.

Synthesis and reactivity of alkynyl boron compounds

Over the last century, there have been considerable developments in organoboron chemistry due to the stability, non-toxicity, and easy commercial availability of various boronic esters. Several organoboron reagents have emerged and play an increasingly important role in everyday organic synthesis. Among them, alkynyl boron compounds have attracted significant attention due to their easy synthesis and diverse reactivity. In this review, we summarize the advancement of research on alkynyl boron compounds, highlighting their importance in the synthesis of valuable compounds.

Synthesis of Indolizine Derivatives Triggered by the Oxidative Addition of Aroyl Chloride to Pd(0) Complex

An efficient synthesis of indolizine derivatives from propargylic pyridines and aroyl chlorides was developed. The 5-endo-dig cyclization was initiated by the in situ formed acylpalladium species from the facile oxidative addition of aroyl chloride to Pd(0) complex. This transformation successfully occurred in the presence of an N-nucleophilic moiety and acid chlorides, a good electrophilic partner, affording highly functionalized indolizines in good-to-excellent yields.

Nickel/copper-cocatalyzed decarbonylative silylation of acyl fluorides

A transformation of acyl fluorides with silylboron via nickel/copper-cocatalysed carbon–fluorine bond cleavage and a sequential decarbonylation, which provides an efficient protocol to functionalize arylsilanes, has been disclosed.

Palladium-catalyzed carbonylative Sonogashira coupling between aryl triazenes and alkynes

We developed a palladium-catalyzed carbonylative Sonogashira reaction with aryl triazenes and alkynes as substrates and methanesulfonic acid as the additive. A series of α,β-ynones were synthesized by this alternative procedure. Notably, bromides, iodides and hydroxyl groups could be well-tolerated under these reaction conditions.

Synthesis, characterisation and reactions of phosphine-substituted alkynylboronates and alkynyltrifluoroborate salts

The synthesis and structural characterisation of phosphine-substituted alkynylboronates is reported. A P(III)-centred alkynylboronate (2) was prepared that showed little evidence for the conjugation of the P-lone pair to the boron via the alkyne π-system, as judged by X-ray crystallography studies of 2 and a related P(V) compound, 3. In addition, corresponding alkynyltrifluoroborate salts were prepared that showed improved stability by comparison to their boronic ester counterparts. These salts undergo Pd-catalysed cross-coupling reactions with aryl halides.