Reduction with tributylstannane

Further research by the same group [229] involved conversion of the lactosamine derivative (337) into the 2 -deoxy- (338) or 3-deoxy- (339) derivatives by conversion of the corresponding alcohols into the phenylthiocarbonate derivatives followed by reduction with tributylstannane. 

A novel method for the reductive deamination of amino-sugars has been published by Barton s group. The process involves sequential iV-formylation, dehydration to the isocyano-derivative, and reduction with tributylstannane. Application of the reaction to l,3,4,6-tetra-C>-acetyl-2-amino-2-deoxy-/3-D-gluco-pyranose afforded 2-deoxy-D-glucose tetra-acetate in 72% yield. 

Geminal dihalides undergo partial or total reduction. The latter can be achieved by catalytic hydrogenation over platinum oxide [512], palladium [512] or Raney nickel [63, 512], Both partial and total reduction can be accomplished with lithium aluminum hydride [513], with sodium bis(2-meth-oxyethoxy)aluminum hydride [514], with tributylstannane [503, 514], electro-lytically [515], with sodium in alcohol [516] and with chromous sulfate [193, 197]. For partial reduction only, sodium arsenite [220] or sodium sulfite [254] are used. 

Sometimes special structural features render possible a reduction of the porphyrin 7r-system. Chlorins 98a were obtained from the Cu complex 97 by nucleophilic addition to a peripheral double bond activated by a nitro group. Reductive denitration occurred on treatment of 98a with tributylstannane. The chlorins 98b can be easily transformed into alkoxyporphyrins 99, which are enol ethers of oxohydroporphyrins and are treated in Section IV,C (84CC1537). 

Reductive cleavage of Aloe groups can be accomplished under Pd 0)-catalysis using various hydride donors such as formic acid,190 tributylstannane,191 phenyl-silane,192 sodium borohydride193 or various borane-amine complexes.194 The reaction gives metal carbamate derivatives and propene as the primary products With tributylstannane the reaction is usually conducted in the presence of acetic... 

In reduction of arenediazonium fluoroborate with tributylstannane, formation of the arene takes place not only by hydrogen atom abstraction from the stannane, but also by reaction of the radical interm iate with the solvent. Reduction of 4-methoxybenzenediazonium fluoroborate with tributyltin deuteride in te-trahydrofuran or acetonitrile affords not only deuterated but also deuterium-free arenes (equation 89). There are also small amounts of biphenyl by-products. ... 

Primary tosylates are reduced by LiAlH4. The diacetal of D-fucose 5.39, an enantiomer of L-fucose, is thus prepared by reduction of tosylate 5.38 derived from the diacetal of D-galactose 5.11. A hydroxyl group can also be replaced by a halogen (Cl, Br, I) at any position of a protected sugar. The halide is easily reduced by a radical mechanism with tributylstannane, Bu3SnH (reaction 5.19). 

Deoxykanamycin B has also been prepared by reduction of the corresponding dichloro derivative with tributylstannane, showing improved activity against Staphylococcus epidermidis ATCC 12228 and Klebsiella pneumoniae 602. It was slightly more active than kanamycin B against strains of S. aureus Apo-1, K. pneu-... 

The same issue is addressed in Table 8, in which reactions of nonracemic substrates are described. Regioselectivity is under steric control. All four acetates 49-52 provide mainly the ( -enantiomer82-83, probably through a common syn,syrt-n-a] yl complex. In most cases, almost 100% chirality transfer is observed. The a-isocyanocarboxylates (Table 8, entries 9, 10)84 are interesting nucleophiles for the preparation of amino acids easily obtained from the alkylated products after acidic hydrolysis. This sequence constitutes an alternative to the Schiff bases of glycine already discussed (see Table 4). Moreover, radical reduction of the isocyano group with tributylstannane yields the a-unsubstituted carboxylic esters. 

Methylquinolinium iodide is reduced by tributylstannane to give mainly the 1,2-dihydro-isomer, which isomerises at room temperature to the 1,4-dihydro-isomer reduction with this reagent but with concurrent irradiation, produced exclusively 1,4-dihydro- 1-methylquinoline, quantitatively." ... 

A new and apparently convenient synthesis of 4-deoxy-D-/> xo-hexose involves reaction of methyl 6-0-benzoyl-2,3-0-isopropylidene-oc-D-mannopyranoside with the adduct formed from imidazole and thiophosgene followed by reduction of the resulting thiocarbamate with tributylstannane (Scheme 4.) Reduction of 1,2 5,6-di-0-isopropylidene-3-0-(methylthio)thiocarbonyl-/3-D-altrofuranose... 

Transformations. Dialkylated A -dimethyldithiocarbamoyl-acetonitriles are transformed into ketones by W-bromosuccinimide bromination or by basic hydrolysis (eq 3), and they are hydrolyzed in acidic ethanol to produce a-mercapto carboxylates. Bromination of (1) in methanol leads to the formation of l,3-dithietan-2-ylium ion. Alkylated N,N-dimethyldithiocarbamoylacetonitriles are reductively desulfurized to a-branched nitriles with tributylstannane in the presence of a catalytic amount of azobisisobutyronitrile (eq 4). ... 

For example, treatment with p-toluenesulfonic acid in methanol affords dimethoxyacetals which can be further hydrolyzed to aldehydes (eq 2). Aldehydes are also available in one step by oxidation of the sulfide to the sulfoxide with m-chloroperbenzoic acid and hydrolytic workup (eq 2). Vinyl ethers are produced via a thermal elimination of benzenesulfenic acid (eq 3). Alternately, the anion formed from the addition of methoxy(phenylthio)methyllithium to aldehydes can be treated with carbon disulfide and iodomethane to form a xanthate which when treated with tributylstannane effects a radical reductive elimination to form (Z)- and ( )-enol ethers (eq 4). ... 

A new mild reaction for the deoxygenation of secondary alcohols has been applied successfully to sugars the reaction, which is radical in character, involves the reduction of a thiobenzoate with tributylstannane (see Scheme 25). Other references to the use of thioesters and the photochemical transformation of dithiobis(thioformates) into thiols are reported in Chapter II, the reaction of cyclic thiocarbonates with methyl iodide to give tu-iodo-iS-methyl thiocarbonates... 

The unsaturated iodo-sugar (48), obtained from 3,4-di-O-benzyl-D-glucal, underwent reductive cyclization with tributylstannane leading to the cyclopentane isomers (49) the cyclohexane derivative (50) was similarly made. ... 

In order to establish the correct absolute stereochemistry in cyclopentanoid 123 (Scheme 10.11), a chirality transfer strategy was employed with aldehyde 117, obtained from (S)-(-)-limonene (Scheme 10.11). A modified procedure for the conversion of (S)-(-)-limonene to cyclopentene 117 (58 % from limonene) was used [58], and aldehyde 117 was reduced with diisobutylaluminium hydride (DIBAL) (quant.) and alkylated to provide tributylstannane ether 118. This compound underwent a Still-Wittig rearrangement upon treatment with n-butyl lithium (n-BuLi) to yield 119 (75 %, two steps) [59]. The extent to which the chirality transfer was successful was deemed quantitative on the basis of conversion of alcohol 119 to its (+)-(9-methyI mande I ic acid ester and subsequent analysis of optical purity. The ozonolysis (70 %) of 119, protection of the free alcohol as the silyl ether (85 %), and reduction of the ketone with DIBAL (quant.) gave alcohol 120. Elimination of the alcohol in 120 with phosphorus oxychloride-pyridine... 

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. 

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