Derivative, tetrabutylammonium

The 6-mono-0-trityl cellulose or the more efficient 6-0-mono-0-(4-monomethyoxytrityl) derivative, and 6-mono-O-TDS cellulose were used to synthesize regioselectively functionalized cellulose ethers at positions 2 and 3 after the exclusive cleavage of the protecting groups (Table 16.10). In case of the trityl derivatives, the deprotection is carried out most efficiently with HCl in a suitable solvent. For TDS protected derivatives, tetrabutylammonium fluoride in THF is most successful for the cleavage of the silyl groups. 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

Moderate yields of the 1- (47%) and 4- (51%) fluoro derivatives of benzo[c]cinnoline were obtained by fluorodenitration of the nitro precursors using tetrabutylammonium fluoride. The 2- and 3-fluoro isomers have been made by Schiemann reactions, though yields were only 25 and 35%, respectively (92SC545). 

In the cyclization of the corresponding cis-epoxides, with the aim of obtaining the corresponding cis-2,3-disubstituted tetrahydropyrans, a similar trend was observed. For these systems, however, the 6-endo pathway was less favored, which was ascribed to difficulties in attaining a TS conformation that would allow for maximum stabilization of the developing p-orbital with the adjacent 7t-system. Alternatively, palladium-catalyzed cyclization of the tetrabutylammonium alkoxide derived from 33b results in the corresponding ris-2,3-disubstituted tetrahydro-pyran in excellent yield and selectivity (90%, dr >99 1), while the ris-epoxide gives stereoisomer 37b (86%, dr 98 2) [112]. 

In the presence of a catalytic amount of tetrabutylammonium fluoride, either freshly dried over molecular sieves22 or as the trihydrate16, silylnitronates 2 derived from primary nitroalkanes react readily at — 78 C or below, via their in situ generated nitronates. with aromatic and aliphatic aldehydes to give the silyl-protected (/J, S )-nitroaldol adducts 3 in excellent yield4,22-24-26,27. Silylnitronates, derived from secondary nitroalkanes. afford the adducts in 30 40% overall yield24. In contrast to the classical Henry reaction (vide supra), the addition of silylnitronates to aldehydes is irreversible. Ketones are unreaetive under such conditions. 

Disodium glyphosate has been reacted with activated heteroaryl halides, such as 2-chlorobenzothiazole or 2-chlorobenzoxazole 79, in aqueous alcohol at reflux to produce the N heteroaryl glyphosate derivadves 80 (2). Improved yields have often obtained in these reactions using the more soluble bis-quatcmary ammonium salt of glyphosate derived from tetrabutylammonium hydroxide (2). 

Ligand 92 was readily prepared by reaction of (+)-pinocarvone with 1-phenacylpyridinium iodide. The authors similarly prepared corresponding 5,6-dihydro-1,10-phenanthrolines derived from (+)-pinocarvone and a tetrahydroquinolone (structure 93, [127]) and obtained up to 81% in the palladium-catalyzed test reaction. Chelucci et al. [ 128] reported the synthesis of chiral Ci-symmetric 1,10-phenanthrolines incorporated in asteroid backbone. Structure 94 derived from 5o -cholestan-4-one in Scheme 51, allowed very high yield and up to 96% ee using BSA and tetrabutylammonium fluoride to generate the malonate anion. 

TABLE 1 Tetra-alkylammonium Ion, R4N, Transferred from W to DCE by the Coupling with the Redox Reaction Between NADH in W and a Quinone Derivative in DCE. Results After Shaking W Containing 10 M NADH and 10 M (R4N )2 SO4 with DCE Containing 10 M Quinone [Q Chloranil (CQ) or Toluquinone (TQ)] for 1 h. TPenA, TBA, and TEA Denote Tetrapentylammonium, Tetrabutylammonium, and Tetraethylammonium ions. Respectively... 

There arises the question as to what causes the upper and lower potentials. The upper potential was found to be the potential of interface o/wl in the presence of tetrabutylammonium chloride in phase o as well as the potential during the induction period. The upper potential should thus derive from a mixed Galvani potential of the transfer of... 

The generated quinone methide intermediates, during the disassembly, are highly reactive electrophiles and rapidly react with any available nucleophile (methanol or tetrabutylammonium hydroxide under organic solvent conditions). We could not isolate any significant amount of material that derived from the core molecule, probably due to generation of a mixture of compounds by the addition of different nucleophiles to the quinone methide. This molecule acts as an amplifier of a cleavage... 

Earlier, the first chiral tetrathiophosphate derivative 311, in which one can recognize 1,3,2-dithiaphospholane subunits, was synthesized in good yield by reacting tetrabutylammonium camphoryl-D-sulfonate (310) with phosphorus pentasul-fide (Scheme 74) [111],... 

To determine if CP was indeed lost in the chemical step the potential was held at — 1.7 V for 30s, then a positive-going scan initiated up to 1.5 V. A number of anodic peaks were observed with the largest and most significant at 1.2 V. This was unequivocally attributed to the oxidation of CP to Cl2 on the basis of a second experiment in which tetrabutylammonium chloride was added to the base electrolyte and the potential regime repeated. Hence, the chemical step after the addition of the first electron involves the ejection of the chloride anion. The identity of the species formed subsequent to this process was determined thus O Toole et al. prepared and characterised the hydrido and acetonitrile complexes (as the bipyridine derivatives) and determined their E° values as —1.46 V and —1.25 V, respectively, far removed from the observed value — 1.62 V hence neither of these species were taken as being the product. 

The 10-57-5-hydridosiliconate ion 62 is known in association with lithium,323 tetrabutylammonium,101 and bis(phosphoranyl)iminium93 cations. It is synthesized by hydride addition to the 8-.S7-4-silane 63, which is derived from hexafluoroacetone.101 Benzaldehyde and related aryl aldehydes are reduced by solutions of 62 in dichloromethane at room temperature101 or in tetrahydrofuran at 0°96 within two hours. The alkyl aldehyde, 1-nonanal, is also reduced by 62 in tetrahydrofuran at O0.96 Good to excellent yields of the respective alcohols are obtained following hydrolytic workup. The reactions are not accelerated by addition of excess lithium chloride,96 but neutral 63 catalyzes the reaction, apparently through complexation of its silicon center with the carbonyl oxygen prior to delivery of hydride from 62.101... 

In a quite different approach, shown in Scheme 204, cycloaddition of nitrile 1232 to trimethylsilyldiazomethane provides silylated triazole 1233, isolated in 75% yield. Treatment with tetrabutylammonium fluoride removes the trimethylsilyl group and simultaneously the silyl protection of the carboxylic group to afford 4-substituted triazole derivative 1234 in 81% yield <2003PEN699>. 

Tetrabutylammonium peroxydisulfate-mediated oxidative cycloaddition was recently discovered to be a convenient method for the realization of fused acetal derivatives. It is believed that the reactive intermediate is the cyclic enol ethers of the 1,3-diketones. An example is presented below <00S1091>. 

Other indoles that have been prepared using the Sonogashira coupling and cyclization sequence include 5,7-difluoroindole and 5,6,7-trifluoroindole [219], 4-, 5-, and 7-methoxyindoles and 5-, 6-, and 7-(triisopropylsilyl)oxyindoles [220], the 5,6-dichloroindole SB 242784, a compound in development for the treatment of osteoporosis [221], 5-azaindoles [222], 7-azaindoles [160], 2,2-biindolyls [223,176], 2-octylindole for use in a synthesis of carazostatin [224], chiral indole precursors for syntheses of carbazoquinocins A and D [225], a series of 5,7-disubstituted indoles [226], a pyrrolo[2,3-eJindole [226], an indolo[7,6-g]indole [227], pyrrolo[3,2,l-y]quinolines from 4-arylamino-8-iodoquinolines [228], optically active indol-2-ylarylcarbinols [229], 2-alkynylindoles [176], 7-substituted indoles via the lithiation of the intermediate 2-alkynylaniline derivative [230], and a variety of 2,5,6-trisubstituted indoles [231], This latter study employs tetrabutylammonium fluoride, instead of Cul or alkoxide, to effect the final cyclization of 215 to indoles 216 as summarized here. 

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