Borohydride tetrabutylammonium reduction

Baeckstrom and coworkers utilized the enhanced selectivity of singlet oxygen towards different types of double bonds, as the key step for the synthesis of trani-Sabinene . By using the method of simultaneous oxidation and reduction (Rose Bengal sensitized photooxidation in the presence of tetrabutylammonium borohydride) they managed to isolate compound 166 by a total conversion of 164 (Scheme 61). Compound 165 remained... 

The allyl glycoside of a-D-Abe-(l ->3)-a-D-Man 115 was prepared by a different approach.200 The ethyl 1-thio-D-abequopyranoside donor 113 was obtained from methyl (3-D-galactopyranoside derivative 110 according to Scheme 33. The cyclic sulfate intermediate 111 was the precursor for the stereoselective reduction with tetrabutylammonium borohydride to 112 which was further derivatized to the thioglycosyl donor 113. Donor 113 was reacted with acceptor 114 to give 115 after deprotection. 

The reduction of tellurium and the alkylation of telluride was carried out in one step using tetrabutylammonium borohydride in refluxing toluene. Dibutyl tellurium was obtained in 95% yield. With tetraethyl-, tetrapropyl-, and tetrahexylammonium borohydride, no reaction occurred2. 

Radical anions can be prepared from phenazines using zinc(II)/potassium hydroxide in dimethyl sulfoxide as the electron source. Phenazine has a relatively high reduction potential and reacts spontaneously with tetrabutylammonium borohydride in benzene or tetrahydrofuran to give the corresponding radical anion. ... 

The reduction of secondary sulfonates with lithium aluminum hydride or sodium borohydride is usually a poor reaction for deoxygenating secondary alcohols [220,222], In most cases, the hydride attack will occur at sulfur and result in cleavage of the S-0 bond to afford the starting secondary alcohol as the main product. An exception from this rule is observed when tetrabutylammonium borohydride is used for reduction of secondary triflates in refluxing benzene [239]. Under these conditions clean displacement with hydride occurs to give the corresponding deoxy compounds in good yield (O Table 14). 

On the other hand, these values are dramatically modified if the presence of alkali-metal (sodium) counterions is taken into account, the ion-paired trianions becoming by far the most stable species (E = —4.5 eV). On this basis, it has been postulated that in the butoxide reduction of 65 and 67 formation of the potassium ion-paired trianions would be favored over that of the ion-paired monoanions, while reduction with tetrabutylammonium borohydride in THF or the electro-... 

Reductions Carbonyl compounds, including conjugated members, acid chlorides, azides, epoxides, and disulfides, are reduced. This salt (1) is a more selective reducing agent than tetrabutylammonium borohydride. 

Fraga et al. [1] smdied the reduction effect of another uncommonly used reductive agent tetrabutylammonium borohydride (NBU4BH4) on similar substrates as well. They found that substrate 3.19 was converted to cts-product 3.20b and trans-product 3.20a under tetrabutylammonium borohydride with 89 % yield (Fig. 3.7). The proportion was 8.2 1. The cis-product was the main product. 

Several examples of reduction by tetrabutylammonium borohydride in the presence and absence of alkyl halide are recorded in Table 12.2. 

Deoxy-l-fluoro-L-glycerol (18) has been prepared by, among other methods, the treatment of 3,4-0-benzylidene-2,5-0-methylene-l,6-di-O-p-tolylsulfonyl-D-mannitol107 (17) with tetrabutylammonium fluoride in acetonitrile, followed by removal of the benzylidene group, periodate oxidation, reduction with borohydride, and hydrolysis. 1,6-Dideoxy-l,6-difluorogalactitol108 was obtained by treatment of 2,3 4,5-di-0-isopropylidene-l,6-di-0-(methylsulfonyl)galactitol with tetra-... 

Chemical reduction of aromatic aldehydes to alcohols was accomplished with lithium aluminum hydride [5i], alane [770], lithium borohydride [750], sodium borohydride [757], sodium trimethoxyborohydride [99], tetrabutylam-monium borohydride [777], tetrabutylammonium cyanoborohydride [757], B-3-pinanyl-9-borabicyclo[3.3.1]nonane [709], tributylstannane [756], diphenylstan-nane [114], sodium dithionite [262], isopropyl alcohol [755], formaldehyde (crossed Cannizzaro reaction) [i7i] and others. 

An alternative procedure is to convert the carbonyl compound into the toluene-p-sulphonylhydrazone,12 followed by reduction with either sodium borohydride in acetic acid,13 or with catecholborane, followed by decomposition of the intermediate with sodium acetate or tetrabutylammonium acetate.14 The former method is illustrated by the conversion of undecan-6-one into undecane (Expt 5.6), and the latter by the conversion of acetophenone into ethylbenzene (Expt 6.4, Method B). A feature of these methods is that with a, / -unsaturated ketones, migration of the carbon-carbon multiple bond occurs thus the tosylhydrazone of isophorone gives 3,3,5-trimethylcyclohex-l-ene, and the tosylhydrazone of oct-3-yn-2-one gives octa-2,3-diene. 

Crossed aldol reaction between an aromatic aldehyde and the TMS enolate of another aldehyde proceeds smoothly in wet or dry DMF using a lithium carboxylate as Lewis base catalyst.158 One-pot conversion to 1,3-diols using sodium borohydride as reductant gives up to 87% yield. A similar report, using tetrabutylammonium phe-nolates as Lewis bases, is diaslereoselective.159... 

However, the displacement reaction of l,2 5,6-di-0-isopropylidene-3-0-p-tolylsulfonyl-a-D-allofuranose with tetrabutylammonium fluoride has been reported to lead to the 3-deoxy-3-fluoro-o -D-glucofuranose derivative. The unexpectedly easy displacement seems to be attributable to freedom from steric hindrance in the n-allofuranose derivative, since the corresponding n-glucofmanose derivative gives only 3-deoxy-l,2 5,6-di-0-isopropylidene-a-D-er2/correlates well with the almost quantitative formation of the D aUo isomer from the reduction of 1,2 5,6-di-0-isopropylidene-a-D-n6o-3-hexulose with sodium borohydride. 

Gold nanoparticles (2.5-7.5 nm diameter) were obtained by Martino and others [402] by reduction of AUCI4 via lithium borohydride in tetrahydrofuran in the reverse micelle system DDAB (didodecyldimethylammonium bromide)/toluene. A purple-colored gold colloid was observable. The particles were encapsulated by silica gels formed in the micellar system by hydrolysis-condensation of TEOS or a prehydrolyzed TEOS, already added in the system. Gelation of silica was achieved by the addition of tetrabutylammonium hydroxide (quicker in case of pre-hydrolyzed TEOS). The particle size was found to be independent of reaction stoichiometry, gel precursor type (TEOS/pre-hydrolyzed TEOS) and the washing step after synthesis. 

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