Lead tetraacetate, and

Separated polyols are detected by a variety of reagents, including ammoniacal silver nitrate (175), concentrated sulfuric acid, potassium permanganate (163), lead tetraacetate, and potassium teUuratocuprate (176). A mixture of sodium metaperiodate and potassium permanganate can be used to detect as htde as 5—8 ).tg of mannitol or erythritol (177). 

The procedure described here serves to illustrate a new, general method for effecting the < -arylation of g-dicarbonyl compounds by means of an aryllead triacetate under very mild conditions. Although the first synthesis of an aryllead triacetate was reported relatively recently, a wide range of these compounds can now be readily prepared. The most direct route to these compounds is plumbation of an aromatic compound with lead tetraacetate, and in the procedure reported here p-methoxyphenyllead triacetate has been prepared in this way. It may also be obtained by reaction of the diarylmercury with lead tetraacetate, a longer, but more general method of synthesis of aryllead triacetates. 

Reaction of Olefins with Lead Tetraacetate and Hydrogen Fluoride... 

Rao prepared 2a-methyl-5a-cholestan-2i -ol (5) by reaction of methyl-magnesium iodide with 5a-cholestan-2-one (4). The 2i -configuration of the hydroxyl group was established by converting (5) to the 2a-methyl-2j5,19-epoxide (6) with lead tetraacetate and iodine in boiling benzene. 

Note 1 Drying of the lead tetraacetate and addition of calcium carbonate do not seem to be necessary for optimum results. 

Lead tetraacetate and periodic acid complement one another in their applicability as reagents for glycol cleavage. The water sensitive lead tetraacetate is used in organic solvents, while periodic acid can be used for cleavage of water-soluble diols in aqueous medium. 

A complementary method is the Kochi reaction. This reaction is especially useful for the generation of secondary and tertiary alkyl chlorides through decarboxylation of carboxylic acids, where the classical method may not work. As reagents, lead tetraacetate and lithium chloride are then employed ... 

Furthermore, photochemically induced homolytical bond cleavage can also be applied when the prepolymer itself does not contain suitable chromophoric groups [113-115]. Upon thermolysis of ACPA in the presence of styrene, a carboxyl-terminated polystyrene is formed. This styrene-based prepolymer was reacted with lead tetraacetate and irradiated with UV light yielding free radicals capable of initiating the polymerization of a second monomer (Scheme 33) [113]. 

A cursory inspection of key intermediate 8 (see Scheme 1) reveals that it possesses both vicinal and remote stereochemical relationships. To cope with the stereochemical challenge posed by this intermediate and to enhance overall efficiency, a convergent approach featuring the union of optically active intermediates 18 and 19 was adopted. Scheme 5a illustrates the synthesis of intermediate 18. Thus, oxidative cleavage of the trisubstituted olefin of (/ )-citronellic acid benzyl ester (28) with ozone, followed by oxidative workup with Jones reagent, affords a carboxylic acid which can be oxidatively decarboxylated to 29 with lead tetraacetate and copper(n) acetate. Saponification of the benzyl ester in 29 with potassium hydroxide provides an unsaturated carboxylic acid which undergoes smooth conversion to trans iodolactone 30 on treatment with iodine in acetonitrile at -15 °C (89% yield from 29).24 The diastereoselectivity of the thermodynamically controlled iodolacto-nization reaction is approximately 20 1 in favor of the more stable trans iodolactone 30. 

Reaction between amides, lead tetraacetate, and acetic acid... 

It seems, however, that di-tertiary glycols are especially reactive Angyal and Young have found that reaction between lead tetraacetate and the di-secondary... 

The structure of the new product from D-glucosamine has also been confirmed by Muller and Varga,7 who oxidized the compound (obtained by Garda Gonz lez) with lead tetraacetate and isolated ethyl 5-formyl-2-methyl-3-pyrrolecarboxylate (XXII), the melting point and other properties of which agreed with those of the compound described by Fischer and Schubert.24... 

Crystalline 1,4-anhydro-D-sorbitol is of much more recent origin than 1,4-anhydro-D-mannitol, inasmuch as its preparation was first recorded in 1946.10 It was obtained by the restricted dehydration of D-sorbitol and has been given the trivial name arlitan. Two groups of workers simultaneously effected proof of its constitution. Hockett and coworkers11 treated the anhydride with lead tetraacetate and since its rate of oxidation coincided with that of ethyl D-galactofuranoside and since one molecular proportion of formaldehyde was formed, the authors concluded that the ring must involve Cl and C4 of a hexitol chain. Assuming that no other carbon atoms are involved, sorbitan is either 1,4-anhydro-D-sorbitol or 1,4-anhydro-D-dulcitol (Walden inversion at C4 of the sorbitol molecule). They therefore synthesized 3,6-anhydro-D-dulcitol (enantio-morphous with 1,4-anhydro-L-dulcitol) but found it to be different from arlitan. 

Oxandrolone Oxandrolone, 17j3-hydroxy-17a-methyl-2-oxa-5-androstan-3-one (29.3.10), is made by oxidation of the C1-C2 double bond of 17j3-hydroxy-17a-methyl-l-androsten-3-one by a mixture of lead tetraacetate and osmium tetroxide with an opening of the A ring of the steroid system, which forms an aldehyde acid (29.3.9). Upon reducing the aldehyde group with sodium borohydride, intramolecular cyclization takes place, directly forming a lactone (29.3.10), which is the desired oxandrolone [31,32]. 

Diacetamides are oxidized by lead tetraacetate, and Hockett and coworkers have studied the behavior of a number of these compounds. 

Furoannelated analogs of uracil acyclic nucleosides were prepared as compounds with potential as anti-HIV agents (HIV = human immunodeficiency virus). Hence, 6-benzyluracil 320 is converted to the precursor 321 first by hydroxymethylation, silylation in situ with bis(trimethylsilyl)acetamide (BSA), then by alkylation (Scheme 28) <2001S559>. Ring closure to 322 was effected by treatment with lead tetraacetate and calcium carbonate <2004AP148>. 

Treatment of amides with bromine in alkaline medium promotes the Hofmann rearrangement, which may or may not involve a free nitrene intermediate." The oxidation of primary amides with lead tetraacetate and the resulting Lossen rearrangement also produces isocyanates, with the possible intervention of an acylni-... 

In Preparation 3-8, use is made of a reagent containing 94 % lead tetraacetate and 6 % acetic acid. If the dry, powdered oxidizing agent is used, the reaction solution must be cooled to —40°C or lower before its addition if comparable results are to be obtained. Yields are definitely reduced if the reaction time is prolonged much beyond 10 sec, and if the steam distillation is not completed within a very short time. For this reason this preparation is probably suitable only if small quantities of product are desired. Yields vary from modest to good for the preparation of nitrosobenzene, p-nitrosotoluene, and p-nitroso-chlorobenzene. An attempt to prepare nitrosocyclohexane by this method did not lead to identifiable products. 

Reaction between amides, lead tetraacetate, and acetic acid 8-17 Reaction between ketones and hy-drazoic acid (Schmidt)... 

The 40-alcohols of the type 2159 with lead tetraacetate and iodine gave, after oxidation of the photolysis mixture, the corresponding lactones (22) as the major product. As illustrated in structure 23, the steric locations of the 40-oxygen atom and the iodomethyl group in this molecule are similar to those in the case of 200-alcohols thus favoring an intramolecular hydrogen abstraction (conversion 11 — 13) over the cycli-zation reaction (conversion 11 —> 12). 

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