Diols with silver carbonate

Concomitant protection of the amino group and the cis-hydroxyl group of the diol 342 was realized by treatment with formaldehyde to afford the oxazolidine 345, oxidation of which with silver carbonate on Celite gave the... 

A corollary of this selectivity is the very easy transformation of diols into lactones with silver carbonate on Celite .16 During the oxidation of a diol with Fetizon s reagent, as soon as an intermediate hydroxyaldehyde is able to equilibrate with a certain proportion of hemiacetal—even if present... 

Diols with primary and tertiary hydroxyls also give lactones on treatment with silver carbonate, but diols with primary and secondary hydroxyls yield, besides lactones, hydroxy ketones, resulting from preferential oxidation at the secondary center (equation 293) [377]. 

In another synthesis the diol 155 was oxidized with silver carbonate on Celite to the lactone 156 convertible (lithium dimethyl cuprate, debenzylation, and dehydration) to ( )-eldanolide [( )-129]. Finally a synthesis of racemic eldanolide involved coupling of a C4 unit, 157, with 4-methyl-3-pentenal. In tetrahydrofuran at -78 C, the reaction occurred at the y-position to the metal atom (158) to yield 72% of the alcohol 159, which gave 98% ( )-129 with mercuric chloride. ... 

It is possible to run a controlled over-oxidation reaction with silver carbonate. Fetizon discovered that 1,3-and 1,4-diols are smoothly oxidized to butyrolactone and valerolactone derivatives in good yield. Oxidation of a diol can be accomplished in the presence of a variety of functional groups, even another alcohol. A primary alcohol, for example, will be oxidized faster than a secondary alcohol, as illustrated by the conversion of 113 to 114.173... 

Draw the structure of the product 9 from oxidation of the diol 8 with silver carbonate on celite. 

A large number of 1,4-, 1,5-, and 1,6-diols is converted to lactones on treatment with silver carbonate on celite in refluxing benzene mevalonolactone is thus prepared in 74% yield. 

Optimum yields of (3-vinyl-y-butyrolactols from the Pd(II) promoted reaction of vinyl triflates with Z-but-2-en-l,4-diol (Scheme 6.33) are attained when tetra-n-butylammonium chloride is added (47]. The lactol is conveniently oxidized to the lactone with celite-supported silver carbonate. The corresponding arylbutyrolactols are obtained in high yield (70-80%) from an analogous reaction of iodoarenes with the enediol. The yields of 2-alkenyl-2,5-dihydrofurans, resulting from the Pd(0) catalysed reaction of cyclic alkynylcarbonates with acrylic esters via tandem C-C and C-0 bond forming reactions, are enhanced by the presence of tetra-n-butyl-ammonium fluoride (e.g. Scheme 6.33) (48]. 

For the synthesis of the tetrasaccharide unit (267) of the blood-group substance A (type 1), Paulsen and Kolar [192, 193] prepared the benzoate (269) by partial benzoyl-ation of the diol (268) and condensed this with 2,3,4-tri-O-benzyl-a-L-fucosyl bromide in the presence of tetraethylammonium bromide to give (270) in 82% yield. The benzoyl group was removed to give (271) and this was condensed with the chloride (274) in the presence of silver carbonate — silver perchlorate to give the tetrasaccha-... 

Oxidation.—Silver carbonate on celite (Fetizon s reagent) reacts non-selectively with a pregnane-18,20-diol (60), giving the lactone (6l) and the lactol (62).82 Special conditions have been described for the selective oxidation of 5a -androstane-3/3,6/3-diol with Fetizon s reagent to give the 3-oxo-derivative as major product. The 3/8,6a-diol readily gives the 3-oxo-derivative in good yield.83... 

Oxidation of the primary alcoholic group to a carboxyl group in diols with primary and secondary hydroxyls is accomplished by silver carbonate [377]. Unfortunately, an extremely large excess of the reagent is needed. Similar results are obtained with a rather exotic oxidant, 4-methoxy-2,2,6,6-tetramethyl-l-oxopiperidinium chloride, which is prepared by treatment with chlorine of a stable radical, 4-methoxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The compound oxidizes 1,4-butanediol to y-butyrolactone in 100% yield (isolated yield 81%) and 1,5-pentanediol to 8-valerolactone in 61% yield (isolated yield 40%) [995] (equation 292). 

By the employment of other bromides O-desmethylmycophenolic acid was obtained. Thus, the C7 bromoester methyl 6-bromo-4-methylhex-4-enoate, BrCH2CH=C(Me)CH2CH2C02Me, was prepared from tritylgeraniol which was first converted in several steps to the terminal diol, Malaprade oxidation of which furnished 4-methy-6-trityloxylhex-4-enal. Mild oxidation to, the corresponding acid with silver oxide, formation of the methyl ester with diazomethane and derivation of the required allylic bromide by treatment of the alcohol, liberated from the trityl derivative, with carbon tetrabromide containing triphenylphosphine completed the synthesis. 

Dioxepan-2-ones (103) have been manufactured from diols, paraformaldehyde, and carbon monoxide in the presence of a copper(I) or silver carbonyl catalyst (Scheme 10). Thus, treatment of CU2O with 98% H2SO4 and CO and reaction with paraformaldehyde and 1,2-propanediol under CO atmosphere gave 5-methyl-l,4-dioxepan-2-one in high yield <89JAP0i09358i>. By the same protocol, l,4-dioxepan-2-one could be obtained by cyclocondensation of trioxane with CO and... 

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