4-hydroxy-3,4-dihydro sodium borohydride

In boiling ethanol, under nitrogen and in the presence of palladized charcoal, 2-acetyl-l,4-dihydro-3-methylquinoxaline (30) undergoes dismutation to give a mixture of 2-acetyl-3-methylquinoxaline, 2-acetyl-l,2,3,4-tetrahydro-3-methylquinoxaline (33), and 2-l -hydroxy-ethyl-3-methylquinoxaline (34), The latter compound is the product of sodium borohydride or Meerwein-Ponndorf reduction of 2-acetyl-3-methylquinoxaline. 

Further reduction of quinones - acquisition of four or more hydrogens per molecule - was achieved with lithium aluminum hydride which reduced, in yields lower than 10%, 2-methyl-1,4-naphthoquinone to 1,2,3,4-tetrahydro-l,4-dihydroxy-2-methylnaphthalene and to l,2,3,4-tetrahydro-4-hydroxy-l-keto-2-methylnaphthalene [931]. Lithium aluminum hydride [931], sodium borohydride, lithium trie thy Iborohydride and 9-borabicyclo[3.3.1Jnomine [100] converted anthraquinone to 9,10-dihydro-9,10-dihydroxyanthracene in respective yields of 67, 65, 77 and 79%. 

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... 

Oxo-2,3-dihydro-4//-benzotellurins were reduced by sodium borohydride in ethanol to 4-hydroxy-2,3-dihydr0-4//-benzotellurins4... 

Hydroxy-2,3-dihydro-4//-benzotcllurln5 13.0 g (50 mmol) of 4-oxo-2,3-dihydro-4 /7-benzotellurin are dissolved in 150 ml of ethanol and 1.2 g (32 mmol) of sodium borohydride is added in small portions to the stirred solution. The mixture is heated on a water bath for 30 min and the product is isolated in the usual manner yield 8.3 g (66%) m.p. 124°. 

Since the reduction of (136) by sodium borohydride in deuteriomethanol resulted in the incorporation (at C-16) of only one deuterium atom the possibility of inversion at C-20 during the reduction is excluded. The oxindole analogue (136) of dihydro-mancunine must therefore also belong to the pseudo series, and C-20 retains its configuration in its formation from dihydrosecologanin. A third representative of the pseudo series is obtained by milder reduction of (136), which avoids both reduction of the ester group and inversion at C-3/C-7, and affords both C-16 epimers of the hydroxy-ester (141). ... 

The 7-0x0 group of 6,7-dihydro-l//,3/i,5/7-pyrido[3,2,l-y][3,l]benzoxa-zine-3,7-dione was selectively reduced to a hydroxy group with sodium borohydride in methanol (87EUP239129 90CPB1575). 

A patent for the preparation of quaternary salts of papaverine from C5, Ce, and Cg halides been published. N-Alkyl-papaverinium salts have been found to undergo oxidation by oxygen either photolytically or in the presence of cuprous chloride, to give the isoquinolones (25). The corresponding dihydro-papaverinium salts (26), with oxygen and cuprous chloride, do not suffer fission, and oxidation of the N-methyl compound (26 R = Me) in this way, followed by reduction of the product with sodium borohydride, affords a- and -hydroxy-laudanosines 21) The n.m.r. spectrum of laudanosine has been studied in detail. 

To a solution of 100 mg (2R)-2-((lR)-hydroxy-l-hept-3-yn-2-one)-l-[((15, 2R)-2-(1-methyl- 1-phenylethyl) cyclohexyoxy) carbonyl]-5-(triisopropylsilyl)-2,3-ciihydro-4-pyridone (0.161 mmol) in 7 mL methanol was added 66 mg cerium(III) chloride heptahydrate (CeCl3 7H20, 0.177 mmol) in one portion. After being stirred for 10 min, the mixture was cooled to —50°C, and 9 mg sodium borohydride (0.241 mmol) was added. The reaction mixture was stirred for an additional 10 min, quenched with 10 mL water, and extracted with CH2CI2 (3 x 10 mL). The combined extracts were dried over MgS04 and concentrated under reduced pressure. The residue was purified by radial PLC (silica gel, 30% EtOAc/hexanes) to give 96 mg (2R)-2-((lR,25)-dihydroxy-hept-3-yne)- -[((15,2R)-2-( 1-methyl- 1-phenylethyl)-cyclohexyloxy)carbonyl]-5-(triisopropylsilyl)-2,3-dihydro-4-pyridone as a colorless oil, in a yield of 96%. 

Racemic trans-l,2-dihydro-l,2-dihydn>xyacronycine (158) was first obtained in very low yield by oxidation of acronydne (2) with chromium trioxide in acetic add followed by alkaline hydrolysis of the intomediate troru-diol monoacetate 274). A more convenient access was recently described 371), based on a previous shufy of the oxidation of acronydne by potassium permanganate 372). Thus, treatment of acronycine (2) with potassium permanganate in aqueous acetone gave l-oxo-2-hydroxy-l,2-dihydroacronydne (376) in 31% yield, accompanied by smaller amounts of c -l,2-dihydro-l,2-dihydroxyacronydne (157) and of the acetone adduct 377. Sodium borohydride reduction of l-oxo-2-hydroxy-... 

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