Oxidations silver® oxide

Thiazol-2-yl radicals have also been generated by silver oxide oxidation of thiazol-2-ylhydrazine in various aromatic solvents (Scheme 69). The... 

Temporary protection of the aldehyde function and reduction with aluminum hydride gave ( )-3-epigeissoschizal (275), from which silver oxide oxidation, followed by esterification, resulted in methyl ( )-epigeissoschizoate (277). 

The silver oxide oxidation of aldehydes to carboxylic acids is aided by the addition of benzyltriethylammonium chloride the active agent is thought to be TEBA-Ag(OH) [16]. 

HLADH oxidation of 3-methylpentane-l,3,5-triol yields, after silver oxide oxidation, (35)-(-l-)-mevalonolactone of 14% optical purity/" The synthesis of [4,5- C2]MVA using known procedures was omitted from last year s Report, " " and another synthesis of ( )-mevalonolactone has been reported. " ... 

Hydroxy- J-qidnones Silver oxide oxidizes derivatives of methyl sesamol 1 to quinones of this type (equation 1). 

In contrast with the relatively facile nucleophilic substitution reactions at the 2-position of the indole system, only 3-iodoindole has been reported to react with silver acetate in acetic acid to yield 3-acetoxyindole (59JOC117). This reaction is of added interest as 3-iodo-2-methylindole fails to react with moist silver oxide (72HC(25-2)127). It is also noteworthy that the activated halogen of ethyl 3-bromo-4-ethyl-2-formylpyrrole-5-carboxylate is not displaced during the silver oxide oxidation of the formyl group to the carboxylic acid (57AC(R)167>. 

As a result of the ring stability of 1,2-benzoselenazoles, ozonolysis of 3-styryI-l,2-benzoselenazole (11) at -30 °C afforded 57% of l,2-benzoselenazo e-3-carbaldehyde (12). Silver oxide oxidation of (12) gave a high yield of l,2-benzoselenazole-3-carboxylic acid (13) which was converted into the amide (14). The amide (14) can be dehydrated to give the nitrile (15). Formation of 3-amino-l,2-benzoselenazole (16) through a Curtius reaction has been reported. The 1,2-benzoselenazole derivative (1) on ozonolysis affords a low yield of the aldehyde (12). 

Further studies on the photochemistry of friedelin have led to the isolation of the unsaturated aldehyde (130).105 Silver oxide oxidation of (130) gave the known putranjivic acid. Irradiation of friedelin in the presence of acetone afforded the hydroxy-ketone (131).106 Photochemically initiated reaction of 7/3-hydroxyfriedelane and 3/3,7/3-dihydroxyfriedelane with lead tetra-acetate-iodine... 

Conversion of some 3-formyl-10-alkylphenothiazines to the corresponding carboxylic acids has been carried out with either alkaline hydroxides or silver oxide. Oxidation of the aldehyde to carboxyl concomitantly with oxidation at the sulfur bridge to the 5,5-dioxide can be effected with alkaline KMn04. ... 

The synthesis of a diseco-cardenolide has recently been reported. The starting material was the threo-ioxm. of the previously known diseco-steroid (507) which was converted into the exo-epoxide (508) by treatment with dimethyl-sulphonium methylide and acetylation. Rearrangement to the aldehyde (509a) with boron trifluoride or stannic chloride was followed by silver oxide oxidation to the acid (509b). This was converted into the a-acetoxy-ketone (509d) via... 

Iodine and silver oxide oxidize alkenes to epoxides [751], whereas iodine and silver ebromate convert alkenes into a-iodoketones [610]. 

Kaneko extended the early work of Schild on tuberostemonine, demonstrating the presence of a C-ethyl group and two lactone rings (1). Edwards et al. 2) used spectroscopic methods to elaborate this picture. Bisdehydrotuberostemonine, the product of silver oxide oxidation 3,4), was shown to contain a pyrrole ring substituted as in I. The NMR-spectrum of this compound confirmed the presence of the C-ethyl group. In addition it was deduced that the second lactone ring was substituted as in II, with a possible further carbon-carbon bond at position 3. 

This isomer of tuberostemonine (mp 120° [ajp —65° (in ethanol) hydrochloride, mp 141 °) was isolated in moderate yield fromiS. sessilifolia Franch. et Sav. 2). It gave bisdehydrotuberostemonine (XVIII) on silver oxide oxidation and the same lactam as tuberostemonine (XX) on oxidation with alkaline permanganate. Hence it only differs from tuberostemonine in the sterochemistry at C-2. 

Scheme 5a. L-p-(3, 4-Dihydroxyphenyl)alanine itself was derived from L-tyrosine either by the action of tyrosinase (ref.39)or by means of silver oxide oxidation.

Tropinone is a low melting tertiary base which readily forms a methio-dide. The decomposition of this methiodide in alkali, in contrast to that of tropine and tropidine, does not give the expected des-base. With potassium hydroxide resinification of the primary product occurs (129) however, with silver oxide (128) or sodium bicarbonate (129) a product thought to be A -dihydrobenzaldehyde (oxime and phenylhydrazone (117)) was isolated in good yield. (This sensitivity towards alkali is a general characteristic of -aminocarbonyl compounds.) Silver oxide oxidizes this aldehyde to a dihydrobenzoic acid, while at elevated temperatures benzoic acid is formed. 

Simple reactions on the substituents can also be performed without destroying the complexes. Thus the aldehyde (CII R=CHO) undergoes borohydride reduction to the alcohol (CII R=CH20H), silver oxide oxidation to the acid (CII R=COOH), and adds methyl magnesium bromide to give the secondary alcohol (CII R=CHOHMe) after hydrolysis. The NMR spectra are consistent with their formulation as (CII) (see Section V, D). The complex (XVIII) thus behaves analogously to ferrocene and cyclopentadienylmanganese tricarbonyl. 

Autooxidation of longifolyl-borane (161), gives besides the expected longifolol (57), products ( 25%) of transannular radical transfer (162) and (163) (108). The silver oxide oxidation of the same borane (46), which also produces (162), (163) is, in fact, only autooxidation. 

In a recent study of the spectroscopic changes that occur during the silver oxide oxidations of dopamine (19), DOPA, 2,4,5-trihydroxyphenylethyl-amine and the dimeric catecholamines (21,22,23,24 and 25). Red solutions exhibiting broad flat maxima in the visible range were observed although the wavelengths of these maxima varied slightly [57-60]. 

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