Introduction of Molecular Complexity via the Cross-Coupling of Lithium 1,4-Dioxene with Aryl Bromides

The synthetic potential of substituted 1,4-dioxenes is well recognised, although the chemistry of 2-aryl-1,4-dioxenes is relatively unexplored. Their transition metal-catalysed synthesis has been limited to Stille-type cross-coupling chemistry, typically showing long reaction times, or proceeding at high reaction temperatures. Here we present a facile and general methodology for the cross-coupling of aryl bromides with lithium 1,4-dioxene, affording a range of 2-aryl-1,4-dioxenes in generally good yields. We highlight the synthetic applicability of this transformation at multigram scale, and demonstrate the versatility of the products by conversion of the dioxene units to various carbonyl-based functionalities. Additionally, we present a concise two-step synthesis of an arylated analogue to a known 1,4-dioxene-based antifungal agent.

Ruthenium-Catalyzed Regioselective Hydrohalogenation of Alkynes Mediated by Trimethylsilyl Triflate

Here we describe a ruthenium-catalyzed regioselective hydrohalogenation reaction of alkynes under mild conditions. Commercially simple halogen sources such as KI, ZnBr₂, and ZnCl₂ were employed to achieve this transformation. Alkynes derived from bioactive molecules such as l-(-)-borneol, l-menthol, and estrone were also suitable for the transformation, demonstrating the potential synthetic value of this new reaction in organic synthesis.

Palladium-Catalyzed Vinylation of Cyclopentenes with Inverted Z,E-Isomerism of Vinylic Substrates

A palladium-promoted Mizoroki-Heck type reaction employing a directing-group strategy to efficiently produce the coupled vinyl cyclopentenes with excellent regio- and stereoselectivity is reported. Typically, a Pd-catalyzed reaction of 2-(cyclopent-2-en-1-yl)-N-tosylacetamide (1a) with (E)-styryl bromides gave cis-2-((Z)-styryl)cyclopent-3-en-1-yl-N-tosylacetamide (3e), an allylic substitution product. Interestingly, we have found that the E,Z-stereochemistry of vinylic substrates is inverted in those products. The mechanism of this catalytic reaction is discussed.

Synthesis of 2,3,4-Trisubstituted 2-Cyclopentenones via Sequential Functionalization of 2-Cyclopentenone

The synthesis of differently substituted 2,3,4-triarylcyclopent-2-en-1-ones from 2-cyclopentenone via sequential functionalization of a novel 2,4-dibromo-3-(4-methoxyphenyl) cyclopent-2-en-1-one intermediate has been developed. The process provides access to selective arylation at C-4 and C-2 with a broader substrates scope, which includes heteroaryl and alkyl substitution at C-2.

Pd-Catalyzed Heck-Type Reaction: Synthesizing Highly Diastereoselective and Multiple Aryl-Substituted P-Ligands

In this work, an efficient palladium-catalyzed Heck-type reaction was successfully used to synthesize a wide range of monoaryl- or diaryl-substituted P-ligands with excellent yields and diastereoselectivity (up to 98% yield, dr >20:1). The preliminary mechanistic studies demonstrated that it possibly underwent a cationic Heck reaction that was assisted by silver salt, and it revealed the significant role of P(O)Ar₂ for excellent yields and diastereoselectivity.

Nickel-catalyzed cross-coupling of β-carbonyl alkenyl pivalates with arylzinc chlorides

The reaction of β-carbonyl alkenyl pivalates with arylzinc reagents was carried out via nickel-catalyzed C–O bond cleavage, forming 3-aryl-substituted α,β-unsaturated carbonyl compounds in moderate to excellent yields.

Efficient synthesis of polymethoxyselenoflavones via regioselective direct C-H arylation of selenochromones

Substantial research has suggested that the configuration and the total number of functional groups on flavones influence their bioactivity. To investigate the changes in the biological activities of selenoflavones in relationship to structural changes, the development of a generally applicable synthetic method was a key. Until now, an efficient pathway for palladium-catalyzed direct arylation with the selenocyclic enone systems is not known in the literature. We herein introduce a simple direct C-H arylation of two difficult coupling partners, selenochromones and electron-rich aryl bromide, affording diverse polymethoxyselenoflavones with great efficiency and high selectivity.

Palladium-catalyzed β-(hetero)arylation of α,β-unsaturated valerolactams

A method for the palladium-catalyzed arylation of α,β-unsaturated valerolactams is reported.

An insight into the synthesis of novel aryl-substituted alicyclic β-amino acid derivatives through substrate-directed palladium-catalysed regio- and stereoselective cross-coupling

Novel aryl-substituted alicyclic β-amino acid derivatives were synthesized through substrate-determined palladium-catalysed cross-coupling of aryl iodides with five- or six-membered cycloalkene β-amino esters.

Controlling olefin isomerization in the heck reaction with neopentyl phosphine ligands

The use of neopentyl phosphine ligands was examined in the coupling of aryl bromides with alkenes. Di-tert-butylneopentylphosphine (DTBNpP) was found to promote Heck couplings with aryl bromides at ambient temperature. In the Heck coupling of cyclic alkenes, the degree of alkene isomerization was found to be controlled by the choice of ligand with DTBNpP promoting isomerization to a much greater extent than trineopentylphosphine (TNpP). Under optimal conditions, DTBNpP provides high selectivity for 2-aryl-2,3-dihydrofuran in the arylation of 2,3-dihydrofuran, whereas TNpP provided high selectivity for the isomeric 2-aryl-2,5-dihydrofuran. A similar complementary product selectivity is seen in the Heck coupling of cyclopentene. Heck coupling of 2-bromophenols or 2-bromoanilides with 2,3-dihydrofurans affords 2,5-epoxybenzoxepin and 2,5-epoxybenzazepins, respectively.