Sodium borohydride trifluoroacetate reactions

The Gribble reduction of diaryl ketones refers to the sodium borohydride-trifluoroacetic acid (NaBHVTFA) reduction of diaryl ketones (1) to diarylmethanes (2).1 The reaction is very general and is applicable to the reduction of diarylmethanols (3) and triarylmethanols (4) to the respective diarylmethanes (2) and triarylmethanes (5).2... 

Fluoroalkjiations are frequentiy performed indirectly using tandem reactions. Arenes react with sodium borohydride in trifluoroacetic acid to afford otherwise difficult to obtain l,l,l-trifluoro-2,2-diarylethanes. Presumably sodium borohydride reacts initially with the trifluoroacetic acid to produce the trifluoroacetaldehyde or its equivalent, which rapidly undergoes Friedel-Crafts-type condensation to give an intermediate carbinol. The carbinol further alkylates ben2ene under the reaction conditions giving the observed product. The reaction with stericaHy crowded arenes such as mesitylene and durene... 

Catalytic reduction of folic acid to 5,6,7,8-tetrahydrofolic acid (225) proceeds fast in trifluoroacetic acid (66HCA875), but a modified method using chemical reductants leads with sodium dithionite to 7,8-dihydrofolic acid (224). Further treatment with sodium borohydride gives (225) which has been converted into 5-formyl-(6i ,S)-5,6,7,8-tetrahydro-L-folic acid (leucovorin) (226) by reaction with methyl formate (equation 70) (80HCA2554). 

Miki and Hachiken reported a total synthesis of murrayaquinone A (107) using 4-benzyl-l-ferf-butyldimethylsiloxy-4fT-furo[3,4-f>]indole (854) as an indolo-2,3-quinodimethane equivalent for the Diels-Alder reaction with methyl acrylate (624). 4-Benzyl-3,4-dihydro-lfT-furo[3,4-f>]indol-l-one (853), the precursor for the 4H-furo[3,4-f>]indole (854), was prepared in five steps and 30% overall yield starting from dimethyl indole-2,3-dicarboxylate (851). Alkaline hydrolysis of 851 followed by N-benzylation of the dicarboxylic acid with benzyl bromide and sodium hydride in DMF, and treatment of the corresponding l-benzylindole-2,3-dicarboxylic acid with trifluoroacetic anhydride (TFAA) gave the anhydride 852. Reduction of 852 with sodium borohydride, followed by lactonization of the intermediate 2-hydroxy-methylindole-3-carboxylic acid with l-methyl-2-chloropyridinium iodide, led to the lactone 853. The lactone 853 was transformed to 4-benzyl-l-ferf-butyldimethylsiloxy-4H-furo[3,4- 7]indole 854 by a base-induced silylation. Without isolation, the... 

Dienes can afford either mono- or di-mercurated products (equations 242 and 243).385-389-391 Mer-cury(II) trifluoroacetate or mercury(II) nitrate are the reagents of choice for this latter reaction. Alkaline sodium borohydride reduction is often accompanied here by formation of unsaturated alcohols. 

Treatment of the product derived from reaction of the iV-oxide 1 with trifluoroacetic anhydride with sodium borohydride gives the tetracyclic indole derivative 2. 

Gribble GW, Leese RM, Evans BE (1977) Reactions of Sodium Borohydride in Acidic Media IV. Reduction of Diarylmethanols and Triarylmethanols in Trifluoroacetic Acid. Synthesis 172... 

Dihydroxylation of the stilbene double bond in the trans isomers of Combretastatin A-1 and A-4 produced diols which by treatment with boron trifluoride in ethyl ether [44] or with trifluoroacetic acid [17] resulted in pinacolic rearrangement to produce an aldehyde. The aldehyde was converted in a variety of derivatives, as illustrated in the Scheme 20, via the following reaction sequence reduction with sodium borohydride to primary alcohol which was derivatized to the corresponding mesylate or tosylate, substitution with sodium azide and final reduction to amine with lithium aluminum hydride. Alternatively the aldehyde was converted to oxime which was catalitically hydrogenated to amine [17]. 

If other reactive moieties are present a cyclopropanecarbonyl compound can be converted to the corresponding cyclopropylalkane using various conditions. Thus, 3,4-benzotricy-clo[4.3.1.0 ]dec-3-en-2-one yielded 3,4-benzotricyclo[4.3.1.0 ]dec-3-ene in excellent yield on treatment with sodium in liquid ammonia. di-l-Methylcyclopropane-l,2-dicarboxylic anhydride underwent a similar reaction to afford isomeric lactones on treatment with lithium aluminum hydride or sodium borohydride in tetrahydrofuran. On the other hand, ionic hydrogenation (triethylsilane in trifluoroacetic acid and water) of cyclopropyl phenyl ketone gave a complex reaction mixture and very little benzylcyclopropane. ... 

The only synthesis published to date by the medicinal chemists Cai et al. was not amenable to scale-up. The discovery route started with the 0-alkylation of 5-iodovanillin (230) with 2-iodoethanol in the presence of K2CO3 and 18-crown-6 ether in DMF to give compound 231 (Scheme 30.41). The Stetter reaction of 3,4,5-trimethoxyphenyl vinyl ketone (232) with aldehyde 231 in the presence of 3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride catalyst (233) and triethylamine in DMF gave the 1,4-dione (234). Reduction of 234 with sodium borohydride in a MeOH-THF mixture gave the corresponding 1,4-diol (235). Diol 235 was cyclized with 5% trifluoroacetic acid in CHCI3 to furnish a mixture of cis and trans isomers of 2,5-diaryl tetrahydrofurans. 

In 1988, Zhang et al. ° achieved the synthesis of the optically active tetracyclic ketone 160, in a stereospecific fashion by employing the asymmetric Pictet—Spengler reaction. Many improvements have been made to prepare both the Na-H and the Na-Me tetracyclic ketones (158 and 160, respectively). The Pictet—Spengler reaction is now carried out in one pot to provide only the desired iraws-diastereomer with high diaster-eoselectivity and enantioselectivity. As illustrated in Scheme 2, after Nb-benzylation of d-(+)-tryptophan methyl ester (156) with benzaldehyde and sodium borohydride in methanol, trifluoroacetic acid (TFA) was added to the reaction vessel at 0 °C to neutralize the reaction mixture. After removal of the solvent, CH2CI2, TFA, and methyl 4,4-dimethoxybutyrate... 

The reaction of an alkene with an alcohol in the presence of a mercury salt such as mercuric acetate or trifluoroacetate leads to an alkoxymercury intermediate, which on reaction with sodium borohydride yields an ether. 

For the preparation of the 2-methylpyrrolo[2,3-b]pyridine derivative, the ten-butyl sarcosine ester derivative,12c(R=r-Bu), was utilized as the tetraester component. Dieclonann cyclizadon of 12c occurred rapidly at room temperature when treated with sodium ethoxide. The resulting anion product was quenched with methyl iodide to afford a mixture of O- and C-methylated products, 15 and 16. The ketonic product 16 was reduced to 17 with sodium borohydride. The resulting alcohol 17, when treated with trifluoroacetic acid at 80, underwent acid catalyzed loss of isobutylene, carbon dioxide, and water to afford the 2-methylpyrrolo[2,3-b]pyridine 18. When this sequence of reactions was run without separating 15 from 16, die trifluoroacedc acid treatment afforded the 3-methoxypyrrolo[2,3-b]pyridine 19 in addition to 18. This result demonstrated that 15 underwent acid-catrdyzed loss of isobutylene and carbon dioxide under these mild reaction conditions. This provided a second method far the synthesis of 3-alkoxy-pyrrolo[2,3-b]pyridines. 

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