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The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.

Unusual observations in the ring-rearrangement metathesis of Himbert arene/allene cycloadducts to form fused polycylic lactams led to a more in-depth experimental study that yielded conflicting results. Differences in reactivity within related systems and unexpected changes in diastereoselectivity among other similar substrates were not readily explained on the basis of the experimental results. Computational investigations demonstrated substrate-dependent changes in reaction pathways (ring-opening metathesis/ring-closing metathesis [ROM/RCM] cascade vs ring-closing metathesis/ring-opening metathesis [RCM/ROM] cascade). Furthermore, some reactions were judged to be under thermodynamic control and others under kinetic control. The greater understanding of the most likely reaction pathways and their energetics provides a reasonable explanation for the previously irreconcilable results.

A Pd(II)-catalyzed reaction protocol was developed for the carboxylation of ortho-C-H bonds in anilides to form N-acyl anthranilic acids. The newly developed reaction procedure provides an efficient pathway for the rapid assembly of biologically and pharmaceutically significant molecules, such as benzoxazinones and quinazolinones, from simple anilides without installing and removing an external directing group.

Monoprotected chiral amino acid ligands is used to perform Pd(II)-catalyzed enantioselective C-H olefination of diphenylacetic acid substrates. The absolute configuration of the obtained olefinated products is consistent with that of a proposed C-H insertion intermediate.

A Pd(ll)-catalyzed reaction protocol for the carboxylation of ortho-C-H bonds in anilides to form N-acyl anthranilic acids has been developed. This reaction procedure provides a novel and efficient strategy for the rapid assembly of biologically and pharmaceutically significant molecules, such as benzoxazinones and quinazolinones, from simple anilides without installing and removing an external directing group. The reaction conditions are also amenable to the carboxytation of N-phenyl pyrrolidinones. A monomeric palladacycle containing p-toluenesulfonate as an anionic ligand has been characterized by X-ray crystallography, and the crucial role of p-toluenesulfonic acid in the activation of C-H bonds in the presence of carbon monoxide is discussed. Identification of two key intermediates, a mixed anhydride and benzoxazinone formed by reductive elimination from organometallic Ar(CO)Pd(ll)-OTs species, provides mechanistic evidence for a dual-reaction pathway. [ABSTRACT FROM AUTHOR]

The article presents a study that describes a palladium (PD)-catalyzed enantioselective carbon-hydrogen (C-H) olefination reaction of α, α-diphenylacetic acids using monoprotected amino acids as chiral ligands. It mentions that the author proposes that σ-chelation of the carbonyl oxygen of carboxylate salt with PD (II) is accountable for the C-H cleavage. The authors screened several monoprotected amino acids and found Boc-Ile-OH to be the optimal chiral ligand.