Oxyls—

Be40(02CCH3)e. The acetate is typical of the basic beryllium carboxylates (Be(OH)2 plus ethanoic acid). The structures have O at the centre of a tetrahedron of Be with carb-oxylate spanning each edge of the tetrahedron. Be(02CCH3)2 is formed from BeCl2 and glacial ethanoic acid. 

A similar intramolecular oxidation, but for the methyl groups C-18 and C-19 was introduced by D.H.R. Barton (1979). Axial hydroxyl groups are converted to esters of nitrous or hypochlorous acid and irradiated. Oxyl radicals are liberated and selectively attack the neighboring axial methyl groups. Reactions of the methylene radicals formed with nitrosyl or chlorine radicals yield oximes or chlorides. 

Acylation of the Leimgruber Batcho enamines with phosgene followed by methanolysis and reductive cyclization generates methyl indole-3-carb-oxylates[8]... 

The regioselectivity of the reaction appears to be determined by a balance of electronic and steric factors. For acrylate and propiolate esters, the carb-oxylate group is found preferentially at C3 of the carbazole product[6-8]. Interestingly, a 4-methyl substituent seems to reinforce the preference for the EW group to appear at C3 (compare Entries 4 and 5 in Table 16.2). For disubstituted acetylenic dicnophiles, there is a preference for the EW group to be at C2 of the carbazole ring[6]. This is reinforced by additional steric bulk in the other substituent[6,9]. 

P4ALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) 9a,21-dichloro-17-[(2-furanyl-carbonyl)oxyl]-llb-hydroxy-16a-methyl-pregna-l,4-diene-3,20-dione. See Mometasone fluroate. 

PREVOST - WOODWARD OlefinHydroxylation CMunctlonalization of alkenes wtfh iodine and silver (or sodium] cart)Oxylates. 

Acetamido-2,2,6,6-tetramethylpiperidine-l-oxyl (acetamidoTEMPO) [14691-89-5] M 213.3, m 144-146, 146-147. Dissolve in CH2CI2. wash with saturated K2CO3, then saturated aqueous NaCl, dry (Na2S04>, filter and evaporate. The red solid is recrystd fi om aqueous MeOH, m 147.5°. [J Org Chem 56 6110 1991 , Bull Acad Sci USSR. Div Chem Set 15 1422 7966.]... 

Cyclohexenone has been prepared by dehydrohalogenation of 2-bromocyclohexanone, by the hydrolysis and oxidation of 3-chlorocyclohexene, by the dehydration of a-hydroxycyclohexa- ione, by the oxidation of cyclohexene with chromic acid or hydrogen peroxide in the presence of a vanadium catalyst, by I lie addition of acroleiti to ethyl acetoacctate followed by cycliza-lion, hydroly.sis, and decar])oxylation, by the reduction of N,N-dimelliyliiniline with sodium and ethanol itt liquid ammonia... 

From indole dibenzyl oxylate, r-BuOK, DMF, reflux, 86% yield. ... 

Thus, in a recent survey of 1509 N-H- 0=C hydrogen bonds in organic carbonyls or carb-oxylates, nearly 80% (1199) were unbrancbed, some 20% (304) were bifurcated, but only 0.4% (6) were trifurcated. Some examples are in Fig. 3.5. 

Tryptophan condenses with a-oxo acids at room temperature to yield l,2,3,4-tetrahydro-j8-carboline-l,3-dicarboxylic acids. Both gly-oxylic acid and pyruvic acid yield the expected products. 

Chemical Name 1 -[2-[(p-chloro-a-phenylben2yl)oxyl ethyl) piperidine Common Name —... 

Chemical Name 2-Hydroxy-5-[ [(4-methylphenyl)sulfonyll oxyl benzenesulfonic acid, piperazine salt... 

Naqvi and Joseph [139] studied the kinetics of acet-oxylation of PVC using 18-crown-6 to solubilize KOAc in organic solvents under mild reaction conditions. They concluded that the substitution of chlorines in PVC by acetoxy groups proceeded by an Sn mechanism. 

Thermal stabilities of modified PVC samples acet-oxylated to varying degrees (reaction temperature 46°C) were determined [45]. Rate of thermal dehydrochlorination at 1% degradation was taken as a measure of thermal stability. The log of the degradation rate is plotted against the acetate content of the polymer in Fig. 2. 

Under irradiation in diethyl ether, the dextrorotary enantiomer of 3,6-hexanooxepin-4-carb-oxylic acid rearranges to the oxabicyclo[3.2.0]heptadiene system with retention of the optical activity.36... 

The reaction of oxepin and 2,7-dimethyloxepin with dimethyl 3-cyano-l,2,4-triazine-5,6-dicarb-oxylate takes the same course as the cycloaddition to the tetrazine. Two different addition products 11a and 12 are obtained in the case of oxepin, whereas dimethyloxepin yields only the [4 + 2] adduct lib.235... 

The inverse electron demand Diels-Alder [4 + 2] cycloadditions of methyl 1,2,4-triazine-3-carb-oxylates 36 (cf. Section B.2.2.) with cyclopropene followed by loss of nitrogen from the unstable cycloadducts 37 provide useful access to 4//-azepine-2-carboxylates 38.83-85... 

Surprisingly, 2,5-dimethyl-3,4-diphenylcyclopentadienone (17) with ethyl l//-azepine-l-carb-oxylate (1) behaves as both diene and dienophile to give a separable mixture of the [4 + 2] 18 and [2 + 4] 19 7t-ewfo-cycloadducts,251 259 the latter being incorrectly formulated in the original paper251 as the opposite regioisomer. l-Mesyl-1//-azepine under similar conditions yields only the [2 + 4] cycloadduct [42% mp 158°C (dec.)],157 251 whereas with tetraphenylcyclopen-tadienone low yields of the [4 + 2] (9.7%) and [6 + 4] (1.7%) rc-adducts are reported.157... 

The imidazol-1 -amine 1 (0.5 g, 2.44 mmol) in hot MeCN (5 mL) was treated with dimethyl acetylenedicarb-oxylate (0.69 g. 4.88 mmol) and the mixture was heated under reflux for 4 h. Evaporation was followed by chromatography of the residue (silica gel. 2% EtOH/benzene) yield 0.38 g (45%) yellow needles (benzene/hexane) mp 113-114 C. 

The yield of the ester 2 in the reaction of tetrasulfur tetranitride with dimethyl acetylenedicarb-oxylate is increased if the reaction is conducted at lower temperatures. The ester is transformed into the parent trithiatriazepine 1 by hydrolysis, followed by decarboxylation of the resulting acid.417... 

Most radicals are transient species. They (e.%. 1-10) decay by self-reaction with rates at or close to the diffusion-controlled limit (Section 1.4). This situation also pertains in conventional radical polymerization. Certain radicals, however, have thermodynamic stability, kinetic stability (persistence) or both that is conferred by appropriate substitution. Some well-known examples of stable radicals are diphenylpicrylhydrazyl (DPPH), nitroxides such as 2,2,6,6-tetramethylpiperidin-A -oxyl (TEMPO), triphenylniethyl radical (13) and galvinoxyl (14). Some examples of carbon-centered radicals which are persistent but which do not have intrinsic thermodynamic stability are shown in Section 1.4.3.2. These radicals (DPPH, TEMPO, 13, 14) are comparatively stable in isolation as solids or in solution and either do not react or react very slowly with compounds usually thought of as substrates for radical reactions. They may, nonetheless, react with less stable radicals at close to diffusion controlled rates. In polymer synthesis these species find use as inhibitors (to stabilize monomers against polymerization or to quench radical reactions - Section 5,3.1) and as reversible termination agents (in living radical polymerization - Section 9.3). 

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