Preparation under phase-transfer

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

The 0,5-dialkyl dithiocarbonates (Table 4.8) are readily prepared under phase-transfer catalytic conditions by the reaction of an alkylating agent with potassium O-alkyl dithiocarbonate [35, 39], which can be obtained from carbon disulphide and the appropriate potassium alkoxide [cf. 40]. Monosaccharides are converted into 5-glycosyl dithiocarbonates via the in situ formation of the tosylate, followed by reaction with potassium O-alkyl dithiocarbonate (Scheme 4.6) [41], In a similar manner, 5-glycosyl 7V,7V-diethyldithiocarbamates are obtained from the monosaccharide and A.A-diethyldithiocarbamate (see 4.3.2) [42]. 

Aroyl cyanides, which have low stability in the presence of water, can be prepared under phase-transfer catalytic conditions in yields >60% [24], A major byproduct of the reaction with benzoyl chloride is a,a-dicyanobenzyl benzoate, resulting from reaction of the benzoyl cyanide with the cyanide ion and subsequent esterification. 

Difficulties arise when the most simple ynediamine bis(dimethylamino)acetylene is prepared starting with trichloroethylene since dimethylamine may react further giving tris(dimethylamino)ethylene 163). A simple one-pot procedure for this ynamine has been elaborated in which trichloroethylene is treated with sodium amide and dimethylamine under normal pressure. The average yield is about 60 %163). Di-chloroacetylene ether complex can now be prepared under phase-transfer (PT) conditions from trichloroethylene. It reacts with dimethylamine under PT conditions to N,N,N"N -tetramethylglycinamide apparently via the ynediamine intermediate 164). 

Adducts of dichlorocarbene and allenes have also been prepared under phase transfer conditions. The product of dichlorocarbene addition to tetraphenylallene is particularly interesting because addition is reported to occur at the C=C double bonds of a benzene ring rather than to the C=C double bond of the allene system. Likewise, the reaction of dichlorocarbene with phenylallene yields an unusual product. In contrast, tetraphenylbutatriene reacts with dichlorocarbene to give a mixture of normal products [31 ]. 

Allylic ethers of aldehyde cyanohydrins have also been prepared under phase transfer conditions [23]. The organic phase, consisting of aldehyde cyanohydrin, an allylic halide (preferably the bromide) and dichloromethane is brought into contact with aqueous sodium hydroxide and tricaprylmethylammonium chloride. Anion exchange in the aqueous phase leads to the tricaprylmethylammonium/hydroxide ion pair, which reacts with the cyanohydrin to form the corresponding alkoxide. Reaction of the alkoxide with the allylic halide leads to the allylic ether of the cyanohydrin (Eq. 7.9). The formation of small amounts of allylic nitriles is apparently due to the side... 

TT-AUyl complexes of cobalt have been prepared under phase transfer catalytic conditions according to equation 9.19 [49]. In a two-phase system consisting of benzene... 

Unsymmetrical a-haloalkyl p-tolyl sulfones have likewise been prepared under phase transfer conditions (see Eq. 13.14) [24]. Thus, a-halomethyl p-tolyl sulfones are deprotonated to form a carbanion which reacts with an alkyl halide to give product. a-Halo-a-sulfonylcarbanions apparently are not prone to undergo facile a-elimina-... 

Polyformals of bisphenols and dichloromethane were prepared by polyetherification in dimethylsulfoxide at 80 °C (22). The poly(formal)s of bisphenol-A, tetramethylbisphenol-A (TMBA), and their copolymers were generated by this method. High molecular weight polymers were obtained, except in the case of TMBA homopolymers where crystallization led to premature precipitation. Incorporation of 70% TMBA afforded an increase in Tg from 88 C to 113 C. The l,4-dihydroxy-2-cyclohexenols were prepared under phase-transfer conditions with dibromomethane (23). These polymers were evaluated as self-developable resists. 

The preparation of pen tanenitrile under phase transfer conditions was described in Section 22 5... 

Naphthaleneacetic acid has also been prepared by the carbonyl-insertion reaction of 1-chloromethylnaphthalene cataly2ed by carbonyl cobalt cation (90,91). Carboxylation of 1-chloromethylnaphthalene in the presence of the catalyst Pd[P(CgH )2]2Cl2 under phase-transfer conditions gave 1-naphthaleneacetic acid in 78% yield (92). 

The benzyne adducts prepared from A -methylpyrrole (and A -methylisoindole) are deaminated conveniently by dichlorocarbene generated under phase-transfer conditions (81JOC1025 to give a convenient route to substituted naphthalenes (134) (and anthracenes) (Scheme 49). 

A mild and effective method for obtaining N- acyl- and N- alkyl-pyrroles and -indoles is to carry out these reactions under phase-transfer conditions (80JOC3172). For example, A-benzenesulfonylpyrrole is best prepared from pyrrole under phase-transfer conditions rather than by intermediate generation of the potassium salt (81TL4901). In this case the softer nature of the tetraalkylammonium cation facilitates reaction on nitrogen. The thallium salts of indoles prepared by reaction with thallium(I) ethoxide, a benzene-soluble liquid. 

Phase transfer catalysis has been used with success to prepare N- substituted pyrazoles (78MI40403, 79MI40408, 70JHC1237, 80JOC3172) and this procedure can be considered the simplest and most efficient way to obtain these compounds. Experimental design methodology has been used to study the influence of the factors on the reaction between pyrazole and -butyl bromide under phase transfer conditions (79MI40408). 

NaH, /7-MeOQH4CH2Br, DMF, —5°, 1 h, 65%. Other bases, such as BuLi, ° dimsyl potassium," and NaOH under phase-transfer conditions," have been used to introduce the MPM group. The use of (n-Bu)4N I for the in situ preparation of the very reactive p-methoxybenzyl iodide often improves the protection of hindered alcohols." In the following example, selectivity is probably achieved because of the increased acidity of the 2 -hydroxyl group ... 

Methylation of indeno[l,2-r/]azepin-4(3//)-one (22) with iodomethane under phase transfer conditions produces the A-methyl derivative, whereas ethylation with Meerwein s reagent yields purple crystals of the indeno[l, 2-r/Jazepine 23, a 147r-aromatic system.57 1 l-Bromo-4-ethoxyin-deno[l,2-r/]azepine (69% mp 143-144°C) can be prepared similarly. 

It is well known that aziridination with allylic ylides is difficult, due to the low reactivity of imines - relative to carbonyl compounds - towards ylide attack, although imines do react with highly reactive sulfur ylides such as Me2S+-CH2-. Dai and coworkers found aziridination with allylic ylides to be possible when the activated imines 22 were treated with allylic sulfonium salts 23 under phase-transfer conditions (Scheme 2.8) [15]. Although the stereoselectivities of the reaction were low, this was the first example of efficient preparation of vinylaziridines by an ylide route. Similar results were obtained with use of arsonium or telluronium salts [16]. The stereoselectivity of aziridination was improved by use of imines activated by a phosphinoyl group [17]. The same group also reported a catalytic sulfonium ylide-mediated aziridination to produce (2-phenylvinyl)aziridines, by treatment of arylsulfonylimines with cinnamyl bromide in the presence of solid K2C03 and catalytic dimethyl sulfide in MeCN [18]. Recently, the synthesis of 3-alkyl-2-vinyl-aziridines by extension of Dai s work was reported [19]. 

Unsymmetrical as well as symmetrical anhydrides are often prepared by the treatment of an acyl halide with a carboxylic acid salt. The compound C0CI2 has been used as a catalyst. If a metallic salt is used, Na , K , or Ag are the most common cations, but more often pyridine or another tertiary amine is added to the free acid and the salt thus formed is treated with the acyl halide. Mixed formic anhydrides are prepared from sodium formate and an aryl halide, by use of a solid-phase copolymer of pyridine-l-oxide. Symmetrical anhydrides can be prepared by reaction of the acyl halide with aqueous NaOH or NaHCOa under phase-transfer conditions, or with sodium bicarbonate with ultrasound. 

In contrast, during the interfacial preparation of poly(iminocar-bonates), the hydrolysis of the dicyanate component regenerates the diphenol component, which is a necessary reactant. Consequently, it is possible to obtain poly(iminocarbonates) simply by the controlled hydrolysis of a dicyanate under phase transfer conditions. 

Substituted furo[3,2-3 4,5- ]dipyrroles 364 were prepared from the appropriate vinyl azides 363 under phase transfer catalyzed conditions (Scheme 76) <1994H(37)1695>. 

Pyrrolizines fused to a pyridine ring can be prepared from pyrrolopyridinones such as 118. These can be alkylated both at the amide nitrogen and at the carbon a to that nitrogen, and so reaction of 118 with l-bromo-3-chloropropane and sodium hydroxide under phase-transfer conditions gives the tetrahydropyrido[2,3-tf]pyrrolizinone 119 <1990BCJ3047> (Equation 6). 

Cyclic dinuclear ylide complexes have also been prepared with sulfur ylides. The reactions of (dppm)(AuCl)2 or (dppe)(AuCl)2 with trimethylsulfoxonium tetrafluoroborate and base under phase-transfer conditions gave the products shown in Scheme 42. Auration of the dppm ligand leads to the byproducts.27... 

Preparation of Copolymers of Vinvlbenzvlacetate and 4(t-BOOstvrene. 4-Vinylben-zyl acetate was obtained from Eastman Kodak or prepared from 4-chloromethylsty-rene by displacement with acetate under phase transfer conditions. 

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. 

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