Preparation under phase-transfer catalysis

Fluonnated allylic ethers are prepared under phase-transfer catalysis (PTC) in the presence of tetrabutylammonium hydrogen sulfate (TBAH) fJ] (equation 2)... 

Preparation of the Active Polvformals under Phase-transfer Catalysis. The polycondensation of DHTN or DHCH with dibromo- or dichloro-methane was carried out under phase transfer catalysis as shown in equations 2 and 3. Best results were obtained with dibromomethane, 60% aqueous KOH and tetrabutyl ammonium bromide. 

A one-pot reaction of phenylacetylene with a dialkyl ditelluride and an alkyl iodide under phase transfer catalysis (method a). The same product can be obtained by using the tellurenyl iodide prepared in situ (method b). ... 

Alkylation of oxazolones with a-halo ketones under phase-transfer catalysis generated an enolate 155 from initial alkylation at C-4 that immediately translac-tonized to produce an enol lactone 156 (Scheme 7.46)." Selected examples of 5(47/)-oxazolones prepared via alkylation are shown in Table 7.17 (Fig. 7.19). 

Compounds 31c and 153 were obtained by direct substitution of the in tf/ -prepared sodium salt of 31a in dimethylformamide (DMF Scheme 15). This method was more efficient <1999CCC321> than the preparation of 31b and 31e from 31a under phase-transfer catalysis conditions <1997MOL69>. 

The mixed sulfates are prepared by transformation of alcohols obtained from D-( + glucose with chloro methyl sulfite into mixed sulfites which are then oxidized with potassium permanganate under phase transfer catalysis into the corresponding sulfates14. 

Apart from some aliphatic iodides, which have been oxidized directly to iodosyl derivatives with ozon or dimethyldioxirane [3], iodoarenes give directly iodylarenes with strong oxidants. From a synthetic point of view, potassium bro-mate in sulfuric acid has been used for the preparation of several members. The parent PhI02 can also be obtained by overoxidation of iodobenzene with peracetic acid, followed by hydrolysis as detailed in Organic Syntheses [36]. Another good method is oxidation of Arl by hypochlorite, at room temperature under phase transfer catalysis (Scheme 7) [37]. 

Alkylthio)isoflavones 758 can be prepared by the reaction of deoxybenzoins with carbon disulfide and alkyl halides under phase transfer catalysis in excellent yield (Scheme 197) <2002TL6113>. 

Another superior method using alkynyl iodonium salts involved the preparation of S-alkynyl O, O-dialkylphosphorodithioates high yields were obtained under phase transfer catalysis [67]. Similarly, with potassium p-toluenethiosulphonate were obtained esters of the general formula p-TolS02SC=CR [68]. 

A similar procedure can be applied to the synthesis of a series of 5-nitroimidazoles83 with antibacterial properties.The S l reaction of various l-alkyl-2-chloromethyl-5-nitroimidazoles (23) with heterocyclic nitronate anions prepared from 3-nitrolactams, under phase transfer catalysis, afforded trisubstituted olefins (equation 33). 

Although the hydrolysis of alkyl halides to alcohols has been extensively investigated, an alternative two-step sequence involving substitution with carboxylate ion is more practical for the preparation of alcohols. Activation of the carboxylate anion prepared by the reaction of the acid with a base can be achieved (i) by use of a polar aprotic solvent and (ii) by use of aprotic apolar solvents under phase transfer catalysis, polymer conditions, or with crown ethers. 

The preparation of orthoformic acid esters from chloroform and alkali metal alkoxides is a long known procedure, " which can be performed under phase transfer catalysis. If small amounts of alcohol are present in the phase-catalyz process, cyclopropanes (372 Scheme 67) can be produced by aHHifinn of dichlorocarbene to l,2-dialkoxy-l,2-dichloroethylenes, which are thought to be intermediates. " Al-kenes of this kind, e.g. (373 equation 176), have been observed as byproducts in the synthesis of tri-r-butylorthoformate from chlorodifluoromethane or dichlorofluoromethane and potassium r-butoxide. Trimethoxyacetonitrile was prepared from trichloroacetonitrile and sodium methoxide. ... 

Cycloimmonium ylides, prepared by interaction of a substituted pyridine with dichlorocarbene generated under phase-transfer catalysis condi-... 

The successful preparation of 1,1-difluorocyclopropanes under phase-transfer catalysis conditions would therefore be possible if difluorocarbene were to be generated within the organic phase where the concentration of hydroxy anions and water is negligible. 

Fluoro-l-iodocyclopropanes are prepared by addition of fluoroiodocarbene, generated from fluorodiiodomethane under phase-transfer catalysis conditions, to alkenes (see Houben-Weyl, Vol. El9b, pp 1504-1505). 

The preparation of mono- and diadducts 5 and 6, respectively, of dibromocarbene with cyclo-hexa-1,4-diene is described. The synthesis of the diadduct encounters difficulties in its isolation, due to the formation of an emulsion and polymeric products. Such problems occur occasionally if an alkene is allowed to react with bromoform under phase-transfer catalysis conditions. 

Phenacyl esters, easily prepared from carboxylic salts and phenacyl bromide under phase transfer catalysis, regenerate the original carboxylic acid by treatment with sodium hydrogen telluride in DMF. ... 

Examples of migratory insertion to aromatic rings also include the total syntheses of anhydrolycorine-7-one (217) [102] and the f-azaebutnane series [103]. As illustrated in Scheme 38, an intramolecular Heck reaction of Af-acylindoline 216 installed the six-membered lactam in anhydrolycorine-7-one (217). In a similar process, the tetracyclic pyrido-[2 ,3 -prepared from bromopyridine 218 under phase-transfer catalysis conditions. Pyridyl indole 219 is a precursor of the pentacyclic skeleton of the E-azaeburnane series. 

The asymmetric alkylation of glycine derivatives is one of the most simple methods by which to obtain optically active a-amino acids [31]. The enantioselective alkylation of glycine Schiff base 52 under phase-transfer catalysis (PTC) conditions and catalyzed by a quaternary cinchona alkaloid, as pioneered by O Donnell [32], allowed impressive degrees of enantioselection to be achieved using only a very simple procedure. Some examples of polymer-supported cinchona alkaloids are shown in Scheme 3.14. Polymer-supported chiral quaternary ammonium salts 48 have been easily prepared from crosslinked chloromethylated polystyrene (Merrifield resin) with an excess of cinchona alkaloid in refluxing toluene [33]. The use of these polymer-supported quaternary ammonium salts allowed high enantioselectivities (up to 90% ee) to be obtained. 

Easy and efficient access routes to heterocyclic complexes are of significant interest in organic chemistry and its application in synthesis in both laboratory and industry. During recent years, several novel routes towards such compounds in aqueous media have been described. 2-Substituted 3,4-dihydro-2H-l,4-benzoxa-zines have been prepared in excellent yields and short reaction times through the cyclization of hydroxysulfonamides in water under phase-transfer catalysis conditions (Scheme 3) [26],... 

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