Lead tetraacetate reaction with diols

The oxidative cleavage of the central carbon-carbon bond in a vicinal diol 1, by reaction with lead tetraacetate or periodic acid, yields two carbonyl compounds 2 and 3 as products. 

Treatment of a solution of 19 in acetone - water with N- methyl morpholine N- oxide and Osmium tetroxide will give the single cis diol which can be cleaved by reaction with lead tetraacetate in benzene to give the sensitive dialdehyde 20. Treatment of 20 with benzylammonium trifluoroacetate in benzene and refluxing will give the alpha,beta unsaturated aldehyde 21. 

Oxidation with lead tetraacetate is a far less selective process.490,491 Studied mainly in the oxidation of cycloalkenes, it gives stereoisomeric 1,2-diol diacetates, but side reactions (allylic acetoxylation, skeletal rearrangement) often occur. A change in reaction conditions in the oxidation of cyclopentadiene allows the synthesis of different isomeric mono- and diesters.492... 

Reactions of 4,7-phenanthroline-5,6-dione have been the subject of considerable study. It is reduced to 5,6-dihydroxy-4,7-phenanthroline by Raney nickel hydrogenation226,249 or by aromatic thiols in benzene,262 and oxidized by permanganate to 3,3 -bipyridyl-2,2 -dicarboxylic acid.263 It forms bishemiketals with alcohols226 and diepoxides with diazomethane.226 The diepoxides by reaction with hydrochloric acid form diols of type 57, R = Cl, which on oxidation with lead tetraacetate give 3,3 -bipyridyl diketones of type 58, R = Cl. Methyl ketones of type 58, R = H, are also obtained by lead(IV) acetate oxidation of the diol 57, R = H, obtained by lithium aluminum hydride reduction of 57, R = Cl. With phenyldiazomethane and diphenyldiazomethane the dione forms 1,3-dioxole derivatives,264,265 which readily hydrolyze back to the dione with concomitant formation of benzaldehyde and benzophenone, respectively. 

These and related reactions of lead tetraacetate have been widely used in synthetic organic chemistry, and are the subject of several reviews.6-10 However, they have found relatively few applications in the carbohydrate field specifically. One important application has been the synthesis of ketones by way of acetoxylation of suitable unsaturated compounds. By treating 1,2-0-isopropylidene-2-propene-l, 2-diol (I) in benzene at 50° with... 

A new synthesis of nojigiku alcohol (773) (Vol. 4, p. 554) starts from tricyclene (774) and we should perhaps recall the preparation of the latter from camphor (40) tosylhydrazone and sodium methoxide in decalin. [Tricyclene is also produced in other reactions leading to camphene (775), such as the reaction of 3-bromocamphor with methylaniline. ] TTie new synthesis consists in anodic oxidation with triethylamine in acetic acid, and yields 76% of 773, with 8% of the endo-isomer and 11% of diols. Oxidation of tricyclene (774) with lead tetraacetate also gives nojigiku alcohol (773), but as a minor (16%) product, the main product being camphor (40). Tricyclene having a plane of symmetry, these methods all lead to racemic 773. 

Oxidative cleavage of 1,2-diols with periodie acid or with lead tetraacetate gives aldehydes or ketones 23,24,25,26,27,39,44,46. A molecule with a particular functional group can be prepared from molecules containing different functional groups by a series of chemical steps (reactions). This process is called synthesis The new molecule is synthesized from the old one (see Chapter 25) 28, 29, 30, 37, 45, 46, 47, 48. 

The reaction between ethyl Hthiopropiolate and the N-acylpyridinium salt formed by reaction of 4-methoxy-3-methyl-5-(triisopropylsilyl)pyridine 2363 with (+)-frafis-2-(a-cumyl)-cyclohexyl chloroformate (TCC chloro-formate) was the starting point in the synthesis of (-l-)-aUopumihotoxin 267A (1718) by Comins et al. (Scheme 301). The dihydropyridone product (—)- 2364 was obtained diastereoselectively (>96%) before hydrogenation to the saturated ester (+)-2365. However, some epimerization of the methyl substituent was apparent after cleavage of the TCC carbamate with lithium methoxide and cyclization to the indolizidinone (—)-2366 (dr 8 1). Acetoxylation at C-8 with lead tetraacetate was stereoselective, and introduced the acetate from the axial direction, possibly by stereoelec-tronicaUy-controUed intramolecular transfer of acetate from a lead—enol intermediate. The acetoxy product (—)-2367 was protodesilylated with formic acid, after which a one-pot tandem reduction with K-Selectride followed by hthium aluminum hydride gave diol (- -)-2368 with complete... 

Quinoxalines 85 have been prepared by the reaction of diols with benzene-1,2-diamines in the presence of a ruthenium catalyst <06TL5633>. Iodobenzene diacetate has been suggested as a less toxic alternative to lead tetraacetate for the oxidative cyclisation of iminooximes to quinoxaline iV-oxides 86 <06TL4969>. 

This reaction pathway is suitable for cis as well as tram diols. In principle, the oxidative cleavage is achieved by lead tetraacetate as well. However, these reagents are complementary, since periodic acid compounds are best used in water and lead tetraacetate in organic solvents. The last step is the reduction of the aldehyde with three equivalents of sodium borohydride to provide alcohol 5. 

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