Catalytic one pot reaction

In 1999, Doye disclosed that dimethyltitanocene is a catalyst widely applicable to intermolecular hydroamination of alkynes with primary aryl- and alkylamines [302]. In the case of unsymmetrically substituted alkynes, the reaction occurs with high re-gioselectivity, forming the anti-Markovnikov products exclusively (Scheme 14.127). Kinetic studies suggest that the reaction mechanism involves the formation of a Ti-imido complex as the catalytically active species. Doye further developed a tandem Ti-catalyzed protocol of alkyne hydroamination and imine reduction, affording secondary amines in a fully catalytic one-pot reaction [303]. 

The original Sonogashira reaction uses copper(l) iodide as a co-catalyst, which converts the alkyne in situ into a copper acetylide. In a subsequent transmeta-lation reaction, the copper is replaced by the palladium complex. The reaction mechanism, with respect to the catalytic cycle, largely corresponds to the Heck reaction.Besides the usual aryl and vinyl halides, i.e. bromides and iodides, trifluoromethanesulfonates (triflates) may be employed. The Sonogashira reaction is well-suited for the synthesis of unsymmetrical bis-2xy ethynes, e.g. 23, which can be prepared as outlined in the following scheme, in a one-pot reaction by applying the so-called sila-Sonogashira reaction ... 

Oxazolines have also been obtained from aziridines and carboxylic imidazolides via iV-acylaziridinesJ1271 Isomerization of the Af-acylaziridines can be achieved by heating with a catalytic amount of tetrabutylammonium iodide or bromide. The transformation can be carried out as a one-pot reaction in quantitative yield (solvents THF, CHC13, benzene) with a wide spectrum of substituents R (R = H, alkyl, c-C6Hi i, C6H5,3-pyridyl). 

Two procedures were developed for C,C-coupling reactions of silyl esters of primary AN. One approach involves two steps and the synthesis of intermediate SENAs according to standard procedures. Another procedure is based on the one-pot reaction of AN with the DBU/TBSOTf system in a ratio of 1 1.1 followed by the addition of silyl ketene acetal and a catalytic amount of TBSOTf. 

Reactions of a,(3-unsaturated acylzirconocene chlorides with stable carbon nucleophiles (sodium salts of dimethyl malonate and malononitrile) at 0°C in THF afford the Michael addition products in good yields (Scheme 5.38). Direct treatment of the reaction mixture with allyl bromide in the presence of a catalytic amount of Cul -2LiCl (10 mol%) in THF at 0 °C gives the allylic ketone in a one-pot reaction. This sequential transformation implies the electronic nature of a,P-unsaturated acylzirconocene chloride to be of type E as shown in Scheme 5.37. 

This chapter surveys different process options to convert terpenes, plant oils, carbohydrates and lignocellulosic materials into valuable chemicals and polymers. Three different strategies of conversion processes integrated in a biorefinery scheme are proposed from biomass to bioproducts via degraded molecules , from platform molecules to bioproducts , and from biomass to bioproducts via new synthesis routes . Selected examples representative of the three options are given. Attention is focused on conversions based on one-pot reactions involving one or several catalytic steps that could be used to replace conventional synthetic routes developed for hydrocarbons. 

Decreasing the number of reaction steps via a one-pot reaction associating two or more catalytic steps. This can be achieved by multistep reactions carried out by cascade catalysis without intermediate product recovery, thus decreasing the operating time and reducing considerably the amount of waste produced. 

Catalytic one-pot procedure. Since in the described teUuronium ylide olefmation tellurox-ide is formed as a by-product, and the telluroxide is susceptible to reduction by triphenyl phosphite, a catalytic procedure can be employed, providing a practical one-pot synthesis of a, -unsaturated esters and ketones (method E). By this procedure, a catalytic amount of n-dibutyl telluride reacts with the a-bromoester or a-bromoketone, and the formed tel-luronium salt is converted in situ under phase transfer conditions (solid KjCOj/trace HjO) into the ylide, which reacts in turn with the aldehyde, giving the olefin. Since the reaction is performed in the presence of triphenyl phosphite, the formed dibutyl telluroxide is reduced back to the dibutyl telluride, which is then recycled. 

With the exceptions of a few rhodium systems (see following), the catalytic pyridine-synthesis relies exclusively on cobalt as the active metal. The reaction can be carried out advantageously in a one-pot reaction by generating the cobalt catalysts in situ [Eq.(2)] (74GEP2416295, 74S575 75USP4006149). 

As an alternative to the stoichiometric enantioselective hydroboration, catalytic hydroboration using chiral catalysts has been also developed for enantioselective hydroboration The catalytic hydroboration-amination methodology has been successfully applied as a one-pot reaction for the asymmetric synthesis of primary... 

The most widely used, and often most convenient reagents for such one-pot reactions are sodium hypochlorite (45) or hypobromite (16). These reactions are performed in the presence of an organic base (generally triethylamine) that normally enhances the yield of cycloaddition products (45). This method was employed for many intermolecular reactions (71) and also seems especially suited for intramolecular ones (72-77) as well as for the solid-phase synthesis (78) of 2-isoxazolines. Hypohalite can also be replaced by sodium broruite in combination with a catalytic amount of tri-u-butyltin chloride (79). In a related method, O-tributylstannyl oximes were treated with tert-butyl hypochlorite to produce nitrile oxides that were trapped with aUcenes or alkynes to afford the corresponding isoxazolines or isoxazoles in moderate to good yield (80). 

Simple one-pot reactions have been developed for the synthesis of 4-bromopyrimidines and condensed derivatives. Under the catalytic influence of dry hydrogen bromide, Al-(cyanovinyl)-amidines cyclized to 4-bromopyrimidines. 2-Aminonitrile compounds with halogenoacetonitri-les gave condensed furopyrimidines in good yields <99H(51)2723>. 

Hijji and Benjamin also accomplished a microwave synthesis of thalidomide in acceptable yield in 2004 (Scheme 5) [36-39]. Ammonium chloride was found to be an effective source for nitrogen. Namely, phthalic anhydride (4), glutamic acid (8), and ammonium chloride were mixed in 1 1 1 ratio with a catalytic amount of DMAP and heated in a conventional microwave oven for 6.5 min. The mixture melted to a brown liquid. The heating continued for an additional 1 min to give thalidomide (1) in 52% yield in this two-step, one-pot reaction after solubilization, precipitation, and recrystal-lization. 

Mulvihill et al. developed a novel one-pot synthesis of 2- or 3-mono-substituted or 2,3-disubstituted quinolines <07OBC61>. In this one-pot reaction, o-nitroaryl-carbaldehydes 80 were reduced with iron and catalytic HC1 to o-aminoarylcarbaldehydes 81 followed by in situ condensation with aldehydes or ketones to form mono- or di-substituted quinolines 82 in good yields. 

Mori has employed transmetallation, well documented in other organozirco-nium reactions [59], to form y-allylated a-silyl allyl amines (Eq. 19) [40,41] and substituted pyrroles (Eq. 20) [60] after the insertion of alkynes into the Zr-C bond of zirconaaziridines. The reaction sequence in Eq. 19 uses stoichiometric quantities of Zr, but catalytic amounts of Cu, and both the insertion and allylation steps proceed with high regioselectivity. Using an acyl halide instead of allyl chloride gives tetra- and pentasubstituted pyrroles, in a one-pot reaction (Eq. 20). 

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