Ozonations acetals, ozone

The synthesis of prostaglandin PGB1 as described by Morin et al. (Eli Lily Research Labs.), starts with 7-(2-methoxyphenyl)heptanoic acid 142 which is converted into 143 through Birch reduction, esterification and acetalization. Ozone cleavage of 143 and cyclization of the resulting dialdehyde affords cyclopentene carbaldehyde 144 which was subjected to ( )-selective Wittig olefination with... 

Oxonium fluorination Perchloryl fluoride. Oxygenation Platinum catalyst. Oxymercuration Mercuric acetate. Ozonization Dimethyl sulfide. 

Oxidation of benzylidene acetals. Deslongchamps has extended his studies on ozonization of acetals to benzylidene acetals. Ozonization of the benzyhdene derivatives (1) of 9/3,lOa-decalin-20,3 -diol in acetic anhydride containing sodium acetate results in formation of a single product (2) with an axial benzoate group and an equatorial acetate group. This is the same isomer that is obtained from the hemiortho ester (3) thus (3) or an equivalent substance is a probable intermediate in the ozonolysis of (1). 

Ozonation of Acetals. Ozone reacts very efficiently with acetals to afford the corresponding esters (eqs 28 and 29). The aldehyde and alcohol components of the acetal function can be varied and yields are excellent. Cyclic acetals react much faster than acyclic acetals as a result of conformational effects. 

New methods for cleavage of benzyl ethers have been reported. Catalytic transfer hydrogenolysis using ammonium formate as donor over palladlum-on-charcoal has been found to work better than with formic acid or cyclohexene over palladium catalysts. Trityl ethers were also cleaved but not benzylldene acetals. Ozone (0 /02,... 

In the presence of tetracyanoethylene, 0x0 compounds can be obtained directly by ozonization of ethylene derivatives. In most cases no side reactions occur.— E A soln. of camphene and tetracyanoethylene in ethyl acetate ozonized at — 70° until a light blue color appears camphenilone (Y 72-80%) and tetracyanoethylene epoxide (Y 81%). F. e. s. R. Griegee and P. Gunther, B. 96, 1564 (1963). 

Aniline Nitric acid, peroxides, oxidizing materials, acetic anhydride, chlorosulfonic acid, oleum, ozone... 

Nitric oxide Aluminum, BaO, boron, carbon disulflde, chromium, many chlorinated hydrocarbons, fluorine, hydrocarbons, ozone, phosphine, phosphorus, hydrazine, acetic anhydride, ammonia, chloroform, Fe, K, Mg, Mn, Na, sulfur... 

Diseleno acetals and ketals are cleaved more rapidly than their dithio counterparts a methyl derivative is cleaved more rapidly than a phenyl derivative. Methyl iodide or ozone converts diseleno acetals and ketals to vinyl selenides. ... 

Other reagents which oxidize acetals such as ozone and TV -bromosuccinimide show similar reactivitjrtrepds. ... 

The acid (3 g) is refluxed with excess acetic anhydride for 45 min, and the excess anhydride evaporated in vacuo. The residue is dissolved in 100 ml. of chloroform and cooled in a bath of ice and hydrochloric acid. With stirring, a solution of 1.45 g of bromine (1 mole) in 50 ml of chloroform is added during 1 hr. Ozonized oxygen is passed through the cold solution until no more ozone is absorbed. The solvent is evaporated in vacuo below 30° and... 

A stream of ozone is passed into a solution of 17j5-hydroxyestr-5(10)-ene-3-one acetate (123a, 4.2 g) in methylene dichloride (17 ml) and methanol (20 ml)... 

P-Hydroxy-A-norpregn-3(5)-en-2-one (7) A solution of the hydroxy-methylene steroid (5) (24.8 g) dissolved in 240 ml of acetic acid and 240 ml of ethyl acetate is ozonized at — 10° with one molar equivalent of ozone. The resulting solution is diluted with 240 ml. of water and 60 ml of 30 % hydrogen peroxide and allowed to stand overnight. The solution is diluted with 1.5 liters of water and extracted with 3 x 700 ml portions of ethyl acetate. The combined extracts are washed with water, saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness under vacuum, leaving 23.4 g of a colorless amorphous residue of crude diacid. This material shows a maximum in the ultraviolet spectrum at 224 mp (s 6,400) indicating a 53 % yield of unsaturated acid (6). It is used without further purification. 

Ozonization of A -steroids usually gives complex mixtures (however, see ref. 48). Ozonolysis became a practical step in the general synthesis of B-norsteroids with the discovery that added methanol" (or formaldehyde ) improves yields significantly. Thus, Tanabe and Morisawa prepared 5/ -hydroxy-6/ -formyl-B-norsteroids (74) from cholesterol acetate, dehydroepiandrosterone acetate and pregnenolone acetate in overall yields of 64-74% by the reaction sequence represented below. 

P-Formyl-B-nor-5 -cholestane-3, 5P-diol 3-Acetate (74). To an ozonized solution of 5 g of cholesterol acetate prepared as above is added 10 g of zinc dust followed by dropwise addition of 40 ml of acetic acid with stirring and... 

Ozone. Most acetals are subject to cleavage with ozone, giving a mono ester of the original diol. 

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