Access to Stereodefined Trisubstituted Alkenesvia Rhodium-Catalyzed 1,4-Addition of Potassium Trifluoro(organo)- borates to Baylis–Hillman Adducts

Rh-Catalyzed Conjugate Addition of Aryl and Alkenyl Boronic Acids to α-Methylene-β-lactones: Stereoselective Synthesis of trans-3,4-Disubstituted β-Lactones

A one-step preparation of 3,4-disubstituted β-lactones through Rh-catalyzed conjugate addition of aryl or alkenyl boronic acids to α-methylene-β-lactones is described. The operationally simple, stereoselective transformation provides a broad range of β-lactones from individual α-methylene-β-lactone templates. This methodology allowed for a direct, final-step C-3 diversification of nocardiolactone, an antimicrobial natural product.

Intermolecular C-O Addition of Carboxylic Acids to Arynes: Synthesis of o-Hydroxyaryl Ketones, Xanthones, 4-Chromanones, and Flavones

An efficient and simple route to biologically and pharmaceutically important o-hydroxyaryl ketones, xanthones, 4-chromanones, and flavones has been developed utilizing readily available carboxylic acids and commercially available o-(trimethylsilyl)aryl triflates.

Chemo- and regio-selective functionalization of Morita–Baylis–Hillman bromides with anthranilic acid

Nucleophilic substitution products of Morita–Baylis–Hillman adducts and their derivatives are valuable synthons. In an attempt to ameliorate the functionality of these functionalized motifs, we report the regio- and chemo-selective functionalization of Morita–Baylis–Hillman bromides with anthranilic acid.

Organometallic catalysts in synthetic organic chemistry: From reactions in aqueous media to gold catalysis

Water has attracted significant attention as an alternative solvent for transition-metal-catalyzed reactions. The use of water as solvent allows simplified procedures for separation of the catalyst from the products and recycling of the catalyst. Water is an inexpensive reagent for the formation of oxygen-containing products such as alcohols. The use of water as a medium for promoting organometallic and organic reactions is also of great potential. This chapter will focus on old and recent developments in the design and applications of some catalytic reactions using aqueous-phase Pd, Rh, Pt, and Au complexes.

The Baylis−Hillman Acetates as a Valuable Source for One-Pot Multistep Synthesis: A Facile Synthesis of Functionalized Tri-/Tetracyclic Frameworks Containing Azocine Moiety

The Baylis-Hillman acetates have been conveniently transformed into tri-/tetracyclic heterocyclic frameworks containing an important azocine moiety via one-pot multistep protocol involving alkylation, reduction, and cyclization sequence.

Heck-type coupling vs. conjugate addition in phosphine-rhodium catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyl compounds: a systematic investigation

The competition between Heck-type coupling and conjugate addition in phosphine-rhodium catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyls has been systematically investigated in a toluene-H(2)O biphasic system. Aside from the intrinsic nature of rhodium and the enolization of carbonyls, the phosphine supporting ligand on rhodium, the ratio of aryl boronic acid to alpha,beta-unsaturated carbonyl and the pH value of the aqueous phase were found to affect the competition significantly. Highly selective rhodium-based catalyst systems have therefore been developed for both Heck-type coupling and conjugate addition by synergistically tuning the supporting ligand, the boronic acid to olefin ratio and other reaction conditions. Conjugate addition with selectivity >99% and Heck-type coupling with selectivity of up to 100%, 98% and 84% for acrylates, acrylamides and methyl vinyl ketone, respectively, could be achieved in the rhodium-catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyls using the corresponding optimized rhodium-based catalyst systems.

BF3·Et2O-Catalyzed Direct Carbon−Carbon Bond Formation of α-EWG Ketene-(S,S)-Acetals and Alcohols and Synthesis of Unsymmetrical Biaryls

A highly efficient BF3.OEt2-catalyzed formal dehydration C-C coupling reaction between readily available alpha-EWG ketene-(S,S)-acetals and various alcohols via direct substitution of the hydroxy group in alcohols has been developed. On the basis of this C-C coupling reaction, a series of alkylated alpha-EWG ketene-(S,S)-acetals and functionalized 1,4-pentanedienes were prepared in high to excellent yields and the unsymmetrical biaryls were synthesized in good yields from the generated 1,4-pentanedienes and nitroalkanes through a one-pot annulation-aromatization process.