Efficient synthesis of racemic and chiral alkenyl sulfoxides by palladium-catalyzed Suzuki coupling

Alkenyl sulfoxide derivatives are obtained in high yields through a palladium-catalyzed Suzuki/Miyaura cross-coupling reaction of racemic and chiral 1-halo sulfoxides with aryl and alkenyl boronic acids. Chiral substrates react with no loss of optical purity and high optical yields. The reaction takes place with different palladium catalysts, such as Pd(PPh₃)₄ or Pd(OAc)₂/DABCO. Although nitrogen ligands like DABCO lead to an active palladium catalyst, they are less effective than the phosphine ones.     

Novel synthesis of 3-(3,3,3-trifluoroprop-1-en-2-yl)furans via stereoselective processing and palladium-catalyzed cycloisomerization

The 3,3,3-trifluoroprop-1-en-2-yl-substituted furans (4) were synthesized via palladium-catalyzed cyclization-isomerization of 1,1,1-trifluoro-2-[(tert-butyldimethylsilyloxy)methyl]-3-alkynylbut-2-en-1-ols (3), which were readily obtained from 1,1,1-trifluoro-2-[(tert-butyldimethylsilyloxy)methyl]-3,3-dibromoprop-2-ene (1) in three steps.     

A highly efficient enantioselective synthesis of 2-methyl chromans via four sequential palladium-catalyzed reactions

An enantioselective synthesis of substituted 2-methyl chromans was accomplished in four steps using four sequential Pd-catalyzed reactions. A study of the key palladium-catalyzed regioselective aryl ether ring formation of two different substrates was also carried out to better understand the factors which affect the selectivity of the reaction.     

A concise synthesis of nornitidine via nickel- or palladium-catalyzed annulation

A concise method to synthesize benzo[c]phenanthridine alkaloid, nornitidine, was developed utilizing nickel- or palladium-catalyzed iminoannulation of an internal alkyne. The advantages of this strategy included readily available starting materials, inexpensive reagents, short reaction steps, and good yields.     

A facile synthesis of aminomethylene bisphosphonates through rhodium carbenoid mediated N-H insertion reaction. Application to the preparation of powerful uranyl ligands

A straightforward procedure ensuring the anchoring of bisphosphonate moiety onto aromatic amines is described. The procedure yields aminoaryl 1,1-bisphosphonates known to display multiple biological activities. The described methodology has also been applied to the synthesis of ligands whose uranyl-binding properties have been studied.     

Regioselective synthesis of trifluoromethyl group substituted allylic amines via palladium-catalyzed allylic amination

The palladium-catalyzed regioselective allylic amination of α-trifluoromethylated allyl acetate occurred using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/DPPF. The selective formation of the γ-product was attained by Pd(OAc)₂/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF₄/DPPF.     

A palladium-catalyzed facile and general method for the stereoselective synthesis of (E)-3-arylidene-3,4-dihydro-2H-1,4-benzoxazines and their naphthoxazine analogues

Palladium-catalyzed cyclocondensation of an aryl iodide with N-tosyl-2-(prop-2′-ynyloxy)aniline at room temperature is shown to constitute a convenient general method for the synthesis of (E)-3-arylidene-3,4-dihydro-2H-1,4-benzoxazines in moderate to very good yields. The method could also be extended to the synthesis of (E)-3-arylidene-2H-naphth[1,2-b][1,4]oxazines. The regio- and stereo-selectivity of the process, short reaction time, operational simplicity, and use of inexpensive starting materials represent its attractive features.     

Pd(0) catalyzed intramolecular alkylation: stereoselective synthesis of furan and isoxazoline-2-oxide analogs

New optically pure isoxazoline-2-oxide and furan analogs have been synthesized using Pd(0) catalyzed intramolecular cyclizations. Starting from a meso-diol, optically pure compounds were prepared without utilizing chiral ligands at any stage of the synthesis. The stereochemical outcome of the product (>99% ee) was influenced by desymmetrization catalyzed by Pseudomonas cepacia lipase and the stereoselective nature of the palladium catalyzed transformations.     

Facile synthesis of 6-iodo-2,2′-dipivaloyloxy-1,1′-binaphthyl, a key intermediate of high reactivity for selective palladium-catalyzed monofunctionalization of the 1,1′-binaphthalene core

A high-yielding procedure for selective monoiodination of 2,2′-dihydroxy-1,1′-binaphthyl (BINOL) is reported. 6-Iodo-2,2′-dipivaloyloxy-1,1′-binaphthyl, obtained in three steps starting from BINOL in 88% overall yield, proved to be a highly efficient substrate in various palladium-catalyzed coupling (Stille, Heck, Sonogashira, and Suzuki coupling) and carbonylation reactions compared to the analogous 6-bromo derivative.     

A mild and efficient palladium-catalyzed homocoupling of lithium alkynyltriisopropoxyborates: a new route to synthesis of 1,3-diynes

Lithium alkynyltriisopropoxyborates were homocoupled in the presence of palladium acetate and DPEPhos. This protocol allows a new efficient route to synthesis of 1,3-diynes under very mild conditions.     

A stereoselective synthesis of digitoxin and digitoxigen mono- and bisdigitoxoside from digitoxigenin via a palladium-catalyzed glycosylation

A convergent and stereocontrolled route to trisaccharide natural product digitoxin has been developed. The route is amenable to the preparation of both the digitoxigen mono- and bisdigitoxoside. This route featured the iterative application of the palladium-catalyzed glycosylation reaction, reductive 1,3-transposition, diastereoselective dihydroxylation, and regioselective protection. The natural product digitoxin was fashioned in 15 steps starting from digitoxigenin 2 and pyranone 8a or 18 steps from achiral acylfuran.     

Synthesis of internal alkynes via one-pot palladium-catalyzed and dehydrobromination reactions of 1,1-dibromo-1-alkenes

Tandem palladium-catalyzed cross-coupling of alkyl, alkenyl, alkynyl, aryl, and heteroaryl 2-substituted 1,1-dibromo-1-alkenes with aryl or heteroaryl boronic acids or borate esters and dehydrobromination of the intermediate coupled products afforded internal alkynes in moderate to good yields (up to 89%). The synthesis has been carried out in a one-pot process and in a two-step sequence according to the nature of the starting 1,1-dibromoalkenes. The reported protocol is compatible with the presence in the 1,1-dibromo-1-alkene molecule of additional reactive halogen–carbon bonds, thus allowing to build up more complex alkyne derivatives.     

Indole synthesis: palladium-catalyzed C-H bond amination via reduction of nitroalkenes with carbon monoxide

Nitroalkenes have been called ‘chemical chameleons’ due to their versatility in numerous synthetic transformations. Herein, we describe the first transition metal-catalyzed transformation of conjugated nitroalkenes into indoles. Under mild reaction conditions (1 atm carbon monoxide, 110 °C), palladium catalyzes the reductive cyclization of nitroalkenes to form a putative nitrosoalkene intermediate, which then rearranges to provide 3-arylindoles in high yields. Notably, this novel C-H bond amination takes advantage of carbon monoxide as an inexpensive stoichiometric reductant and produces carbon dioxide as the major byproduct.     

Synthesis of jaspine B regioisomers through palladium-catalyzed stereoselective tetrahydrofuran formation: Insight into the ligand recognition of sphingosine kinases

We recently reported a structure-activity relationship study of 4-epi-jaspine B derivatives toward sphingosine kinase (SphK) and identified selective inhibitors of two SphK isoforms. In this study, we designed and synthesized jaspine B regioisomers on the basis of palladium-catalyzed tetrahydrofuran formation and late-stage cross metathesis reactions to investigate the influence of the substitution position of functional groups on SphK inhibition. Evaluation of the jaspine B regioisomers SphK inhibitory activities revealed that several of these compounds exhibited comparable SphK1/2 inhibitory potency to that of 4-epi-jaspine B.     

Novel stereoselective synthesis of spiroketal structure using Pd(II)-catalyst

We report a highly stereoselective palladium(II)-catalyzed intramolecular cyclization of 1,11-dihydroxyundec-9-en-5-one derivatives via unstable hemiacetal intermediates, in which cyclization occurs without activation of the allylic alcohol to afford spiroketal structures.     

Green synthesis of fluorinated biaryl derivatives via thermoregulated ligand/palladium-catalyzed Suzuki reaction

Fluorinated compounds have attracted considerable attention in pharmaceuticals, agrochemicals and material science due to their unique physical properties. This paper reports an efficient and environmentally benign protocol for the Suzuki reaction of aryl halides with fluorinated arylboronic acids over a thermoregulated ligand/palladium catalyst using water as sole medium, affording a variety of fluorinated biaryls, including fluorinated liquid crystals, in excellent yields. The catalyst could be recycled four times with high activity. The active catalyst was proved to be a palladium/ligand complex via a mercury-poisoning test.     

Towards a facile synthesis of triarylethanones: palladium-catalyzed arylation of ketone enolates under homogeneous and heterogeneous conditions

The palladium-catalyzed regioselective α-monoarylation of deoxybenzoins and α,α-diarylation of acetophenones provides general, efficient access to 1,2,2-triarylethanones. After a comprehensive search for suitable experimental conditions to optimize such transformations, both reactions are alternatively conducted by means of either commercially available polymer-anchored catalysts or a very simple homogeneous catalytic system, thus avoiding the use of complex ligands. In addition, the synthesis of deoxybenzoins employing polymer-supported fibrous palladium catalysts is reported for the first time, and the excellent catalyst recycling properties suggest applicability to industrial purposes.     

Electrochemical synthesis of geminal azidonitro compounds

An electrochemical method for the synthesis of geminal azidonitro compounds was developed. The method involves electrooxidative coupling of azide anions with salts of nitro compounds and affords geminal azidonitroalkanes, azidonitrocycloalkanes, and diazidodinitrocycloalkanes in 45–92% yields.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2452–2457, November, 2004.     

Novel and stereoselective asymmetric synthesis of an amino sugar analogue, furanodictine A

A novel and efficient strategy is described for the asymmetric synthesis of the first 3,6-anhydrosugar to be isolated from natural sources, furanodictine A. The synthetic process is based on requisite stereodefined manipulation of the functionalized amino alcohol obtained through nucleophilic addition of vinyl Grignard reagent to the aminal incorporating the d-arabinofuranose-derived skeleton in a complete stereoselective manner.