Sodium tosylate reduction with

Reduction of alkyl halides and tosylates. - Reduction with sodium cyanoborohydride in HMPT provides a rapid and selective removal of iodo. bromo, and tosyloxy groups in high yield. Thus 1-iododecane can be reduced in thi.s way to n-deeane in... 

Ethenylcyclopropyl tosylates 131 and 2-cyclopropylideneethyl acetates 133, readily available from the cyclopropanone hemiacetals 130, undergo the re-gioselective Pd(0)-catalyzed nucleophilic substitution via the unsymmetrical 1,1-dimethylene-jr-allyl complexes. For example, reduction with sodium formate affords a useful route from 131 to the strained methylenecyclopropane derivatives 132. The regioselective attack of the hydride is caused by the sterically... 

The pyrrolidine derivative 314, a skeletal analog of the antitumor antibiotic anisomycin, was synthesized from the acetal derivative 16b. The 5-OH group of 16b was tosylated and then substituted with sodium azide. Reduction (sodium borohydride) of the lactone group afforded an open-chain derivative, which was selectively protected to give 313. Hydrogenation of the azide function, followed by p-toluenesulfonylation, led to 314 by an intramolecular nucleophilic displacement (284). 

The 1-isopropoxymethyl derivative of pyrrolo-benzothiazepine 376 can be obtained from aldehyde 375 through the tosyl hydrazone followed by reduction with sodium borohydride in 2-propanol. 1-Methyl substituted 378 is available from aldehyde 375 and hydrazine monohydrate followed by potassium tert-butoxide (Scheme 76, Section 5.1.1 (2004JMC143)). 

The keto group in condensed 4//-pyran derivative 264 was successfully reduced by reduction of the tosyl hydrazide with sodium borohydride.290... 

Methyl-D-fucose has been prepared by two methods.68 In the first, methyl a-D-galactopyranoside was converted into the 6-tosyl derivative, from which by condensation with acetone methyl 3,4-isopropylidene-6-tosyl-a-D-galactopyranoside (LXIV) was obtained. Methylation gave the corresponding 2-methyl ether which was converted into the 6-deoxy iodide (LXV) by heating with sodium iodide in acetone solution at 140°. Reduction with Raney nickel gave sirupy methyl 2-methyl-3,4-isopro-pylidene-a-D-fucopyranoside (LXVI) from which 2-methyl-D-fucose was obtained on hydrolysis. 

The resulting acetate 116 is formulated as the tawis-isomer, too. The carboxylic group was then converted by selective reduction with diborane to the alcohol 117. The alcohol function was converted to the nitrile 119 via the tosylate 118 and displacement of the tosylate group with sodium cyanide. Methanolysis led to the methylester 120 because the acetate moiety was not cleaved under these conditions (MeOH/HCl). Hydrolysis with base yielded the deprotected lactone acid alcohol 121, which was purified by converting it into the methylester 122. 

Derivatives of 1-methyl-3//-l,4-benzodiazepine-2,5(l/I,4/I)dione (193) were synthesized by ring closure of substituted 2-(A-chloro-acetyl-A-methylaminoJbenzamides with sodium methoxide in methanol.209 Treatment of 193 with lithium aluminum hydride led to reduction of both carbonyl groups.209 The parent tetrahydro system (194) has been prepared by reaction of the tosylate (195) with 1,2-dibromoethane followed by hydrolysis.210 The preparation of 194 by another route had previously been noted.204 Reaction of 194 with formaldehyde or benzaldehyde gave a compound formulated as 196 (R = H or C6H5).210 Hydrolysis of 196 (R = C6H5) with 0.1 N hydrochloric acid gave 194 while 196 (R = H) was not hydrolyzed at this acidity. 

The /3-hydroxy 4-methylbenzenesulfonamides are useful intermediates. For example, those produced from (E)- and (Z)-5-decene were converted in two steps to cis- or fran,s-2,3-dibutyl-l-(4-methylphenylsulfonyl)aziridine, respectively. Furthermore the A-tosyl group can be removed by reduction with sodium in ammonia76. 

Reduction with sodium/liquid anunonia was introduced 70 years ago for the removal of benzyl-type and tosyl protecting groups and still remains a weU-estabhshed protocol in peptide synthesis.P Benzyl esters are also cleaved with tcrt-butyldimethylsilane in the presence of palladium(II) acetate yielding the corresponding TBDMS esters which are readily hydrolyzed in the presence of ACOH/H2O (see Section 2.2.1.3).P ... 

A final method of alkene formation from a-derivatized ketones entails formation of unsaturated tosyl-hydrazones from a,P-unsaturated ketones followed by conjugate reduction with sodium cyanoborohy-diide in acid media. This transformation, which proceeds with regioselective migration of the original double bond, has been applied to the synthesis of quassinoids by Ganem et al. (Scheme 22). A similar... 

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]. 

The 5"-hydroxy group of neomycin B was converted to an amino group by treatment of the 5"-tosylated derivative with sodium azide, followed by reduction of the azide to the amino group by triphenylphosphine in the presence of an aqueous solution of sodium hydroxide. The resulting 5"-amino neomycin B was shown to be a better RNA binder, slowing down the ribozyme cleavage more effectively than the parent compound [73]. 

The synthesis of 3-benzoyl-A-homo-3-aza-5) -androstan-16-one (37), an analogue of the alkaloid samanine (36) from Salamandra maculosa, has been reported. Sodium borohydride reduction of the known compound (38) followed by tosylation alTorded the tosylate (39) the nitrile group was reduced by diborane and cyclized by benzoic anhydride-pyridine to the derivative (40a) similar cyclization with acetic anhydride-pyridine yielded the related acetamide (40b). This cyclization requires one equivalent of anhydride and the uncyclized amide is not an intermediate in the reaction. Jones oxidation of (40a) was followed by conversion into a benzylidene ketone derivative (41) with benzaldehyde-KOH in methanol. Reduction of (41) with sodium borohydride and acetylation furnished (42). Treatment of compound (42) with ozone followed by mild zinc reduction produced an acetoxy-ketone, which was further reduced by Zn-HBr-CH2Cl2 to the ketone (37). 

The reductive ring opening of 330a with sodium cyanoborohydride/titanium tetrachloride in acetonitrile occurs with no ester reduction whatsoever to provide 421 in 83% yield. Subsequent conversion to the tosylate followed by reduction with lithium borohydride/lithium triethylborohydride affords in 61% yield the crystalline diol 422. Lithium aluminum hydride or sodium borohydride reduction of the tosylate of 421 fails to produce clean reductions to 422. Epoxide ring closure of 422 is achieved with two equivalents of sodium hydroxide in methanol to fiimish in 93% yield (2 S, 3i )-2-benzyloxy-3,4-epoxybutan-l-ol (423) [140] (Scheme 94). 

The cyclohexylidene protecting group has been employed in several syntheses. A preparation of 2,3-0-cyclohexylidene-4-deoxy-L-threose (445) fi om L-( + )-diethyltartrate (lb) in seven steps illustrates one synthetic application (Scheme 99). Conversion of the monobenzyl protected alcohol 443 to its tosylate followed by reduction with sodium borohydride provides the deoxy intermediate 444, which is reductively deprotected and Swem oxidized to 445 in good overall yield. Treatment with benzylamine provides an imine that undergoes a stereoselective carbon-carbon bond forming reaction with a-lithio-A, A -dimethylacetamide in the presence of the Lewis acid zinc bromide to furnish, after Cbz-amine protection, the j9-aminoamide 446. This is converted in four steps to A -acetyl-L-daunosamine (447), a sugar moiety particularly important as the carbohydrate constituent of the anthracycline antibiotics [149]. 

Tosyl group (Tos), 4-toluenesulfonyl group, Tos, a sulfonamide-type protecting group for N , the Arg guanidino group, or the His imidazole nitrogen. It can be cleaved by reduction with sodium in liquid ammonia. 

Dihydropyran derivatives were synthesized as follows 2-(tosyloxymethyl)-3,4-dihydro-2H-pyran was prepared by the reaction of tosyl chloride with 2-(hydroxymethyl)-3,4-dihydro-2H-pyran, which was obtained by reduction of 2-formyl-3,4-dihydro-2H-pyran, Diels-Alder product of acrolein, with the aid of NaBH4. Syntheses of 2-(nucleic acid base methyl)-3,4-dihydro-2H-pyrans were achieved by treatment of sodium salts of the corresponding nucleic acid bases with 2-(tosyloxymethyl)-3,4-dihydro-2H-pyran in dimethylformamide. In order to facilitate its copolymerization with maleic anhydride, the amino group of adenine was blocked by acetyl group. 

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