Reductive acetylation

The l,3-dioxol-2-one ring in these compounds is relatively stable, thereby allowing acetylation, reduction, and the replacement of the keto group by a thione group giving photochromes 243-245 (02IZV1588, 05IZV1299). 

Acetonitrile, 407 Acetophenone, 725,729,730 phenylhydrazone, 852 p-Acetotoluidide, 593, 605 Acetoxime, 343 Acetylacetone, 861, 862, 863 Acetylation, reductive, 749 Thiele, 749 Acetyl chloride, 367 2-Acetylcyciohexanone, 862, 864 Acetylene, 245, 897 reactions of, 245, 246 Acetylenic compounds, synthesis of, 467-469, 895-902 Acetylglycine, 909 Acetylmethylurea, 968, 969 Acetylsalicylio acid, 996 Acetyl-o-toluidide, 578 2-Acetylthiophene, 837 Acid anhydrides of aliphatic carboxylic acids, 371... 

O-Benzylation of 148 with benzyl bromide in the usual manner yielded the tri-0-benzyl derivative (149), [a]p7 —0.8° (chloroform). On hydrolysis with aqueous acetic acid, 149 gave the compound (150), which was further converted to the compound (151) by sodium borohydride reduction. Periodic acid oxidation of 151 and successive sodium borohydride reduction gave 5,6-di-<9-acetyl-2,3,4-tri-0-benzyl-pseudo-a-L-altropyranose (152), [a] 6 —25.7° (chloroform), after conventional acetylation. Reductive cleavage of 152 with sodium in liquid ammonia and subsequent acetylation afforded pseudo-a-L-altropyranose pentaacetate (153), m.p. 84-85 °C, [ ]q6 —13.7° (chloroform). Hydrolysis of 153 gave 154, [ot] —43.6° (methanol) [35] (Scheme 24). 

Zard and coworkers have developed a synthesis of substituted dienes by reductive elimination of ally lie nitroacetates (equation 33). Ally lie nitroacetates can be prepared by condensation of nitromethane with the carbonyl compound followed by addition of formaldehyde and acetylation. Reductive elimination can be carried out by employing either chromous acetate or samarium iodide. 

The acetylation/reduction protocol was also applied to monocyclic azetidin-ones by this route, the tritylthio derivatives 185 and 189 were hydroxyethylated to 188 [116] and 190 [51a]. Alternatively, formylation (LDA/ethyl formate) followed by methylation (MeLi/CuI) converted 185 to 188 in 65% overall yield [51]. 

Tritylthioazetidinone-phosphoranes unsubstituted at C3, either racemic (from 4-acetoxyazetidinones) or optically active (from 6a-bromopenams), were key intermediates in the Bristol penem programme in fact, they proved good substrates for the introduction of the (li )-hydroxyethyl sidechain by the acetylation-reduction sequence [51a]. Hydroxyethylated argentiothioazetidin-ones 229 are no longer obtained by this way, but have retained their original... 

Acetylation is mainly applied to stabilize the cell wall against moisture absorption for improving its stability and environmental degradability [48-52]. In acetylation, acetic anhydride substitutes the hydroxyl group of the cellulose with acetyl groups that modify the properties of fibers so that they become hydrophobic [50]. Moisture absorption of fiber reduces after acetylation, which is beneficial for composites application. It was reported that after acetylation reduction in moisture uptake was found to be around 50-65% [53]. 

The synthesis of vinylruthenocene VR and vinylosmocene VO requires acetylation, reduction and dehydration by pyrolysis from alumina (Scheme 2), The procedure of Hill and Richards was used rather than more conventional acetylation with acetyl chloride and aluminum chloride because it gave near quantitative yield of acetylruthenocene with no formation of 1,1 - diacetylruthenocene In the case of osmocene acetylation is only 70-80% complete. Increasing the reaction time produces extensive decomposition. Thus chromatography is required to remove the tar formed and to separate osmocene and acetyl-osmocene. In general higher temperatures and longer reaction times are required for osmocene as compared to ferrocene and ruthenocene, in agreement with previous observations. 

The //3-sulfido cluster 118a is also accessible via sequential acetylation-reduction of the complex 142,... 

Terminal acetylenes are often used as precursors to the E- and Z-olefins. A typical synthesis is that reported by Schwarz and Waters (187) (Scheme 80). The alkali metal salt of the acetylene is coupled with an appropriate alkyl halide to give the acetylenic tetrahydropyranyl ether (444). Sodium in liquid ammonia reduction of the ether stereo-specifically affords.pure -olefins, which can be hydrolyzed to an alcohol and then acetylated. For Z-isomers, the protecting group must first be removed and the alcohol acetylated. Reduction over quinoline-poisoned... 

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