Mercury , oxidative cyclization

As described in Chapter III, morusin (3) has been found to be anti-tumor promoter in a two-stage carcinogenesis experiment with teleocidin. Considering the similarity of the structures between morusin (3) and artonin E (7), artonin E (7) was expected to be an anti-tumor promoter. Furthermore we found a novel photo-oxidative cyclization of artonin E (7) as follow photo-reaction of artonin E (7) in CHCI3 containing 4% ethanol solution with high-pressure mercury lamp produced artobiloxanthone (8) and cycloartobiloxanthone (9), and the treatment of artonin E (7) with radical reagent (2,2-diphenyl-1-picrylhydrazyl DPPH) resulted in the same products, Fig. (15), [84]. 

Mercury salts, such as mercury(II) acetate,521-525 mercury(II) oxide,524,526-528 metcury(II) trifluoroace-tate,529,530 mercury(II) sulfate524,531 and mercury(II) phosphate531 catalyze the addition of carboxylic acids to alkynes. Acetic anhydride in the presence of boron trifluoride etherate can also be effectively used in this reaction (equation 292).521,522 Alkynoic acids undergo mercury-catalyzed cyclization to lactones (equation 293).523,532,533... 

Diazahexatriene systems generated on a uracil spacer molecule are cyclized to give 6-aryllumazines [76H(4)977,76H(4) 1659 77JCS(P1)1336]. Another approach to a lumazine is accomplished by oxidative cyclization of 6-amino-5-hydroxyethylidene-aminouracils with mercury(II)chloride (79CPB1094, 79H359) (Scheme 52). 

Oxidative cyclizations [1, 652, before references] have been realized by Julia, Colomer, and Julia38 by treatment of certain phenyl-substituted olefins with mercuric acetate. 4-Phenyl-1-butene (1) on treatment with mercuric acetate in acetic acid, followed by treatment with perchloric acid, gives a mixture from which the three products formulated were isolated in the low yields indicated (some metallic mercury is deposited). 

MI1 74MI7). The acetates of these acydo C-nucleosides (539, R = Ac) were obtained by oxidative cyclization of the Schiff bases 540, derived from aldehydo-sugar acetates 180 and 4,5-diimino-l,3-dimethyluracil, with mercury(II) chloride in dimethyl sulfoxide [79CPB1094, 79H(12)359] (Scheme 144). 

The key step in the preparation of the inhibitor is shown in Scheme 1.4.10 and involves the elaboration of the glucose derivative, shown, to the olefin on reaction with methylenetriphenylphosphorane. Once the olefin was isolated, the C-glycoside was obtained via mercury mediated cyclization followed by oxidation of the mercury with iodine. Further elaboration of the resulting iodide gave the desired C-phosphate disaccharide shown. 

Oxidative cyclization of (Z)-30 with mercury (II) acetate produced an oxazoline (A). 

Triaza-Compounds. 2-(Ethoxymethyleneamino)pyridine is converted into the triazolopyridine (564) by the action of hydroxylamine-O-sulphonic acid. Anodic oxidation of the hydrazone Ar NHN=CHAr (Ar =p-NO2C6H4, Ar = /7-MeC6H4) in the presence of pyridine and tetraethyl-ammonium perchlorate affords the salt (565). Oxidative cyclization of the pyridylhydrazone PyCH=NNHPy (Py = 2-pyridyl) by means of mercury(II) acetate yields compound (566). 2,4,6-Triphenylpyrylium fluoroborate reacts with amidrazones ArC(NH2)=NNH2 in the presence of triethylamine to give the pyrazolopyrimidines (567). The tricyclic compound (568) is... 

Cacchi and Palmier (83T3373) investigated a new entry into the quinoline skeleton by palladium-catalyzed Michael-type reactions. They found that phenyl mercurial 134 was a useful intermediate for the synthesis of quinoline derivatives, and that by selecting the reaction conditions the oxidation level of the heterocyclic ring in the quinoline skeleton can be varied. On such example is shown in Scheme 16. PdCla-catalyzed coupling between organomercurial reagent 134 and enone 135 delivered adduct 136 which was subsequently cyclized to quinoline 137 under acidic conditions. 

The cyclized analog of meralluride is prepared by a similar synthesis. Thus, condensation of camphoric acid (42) (obtained by oxidation of camphor) with ammonia gives the bicyclic succinimide (44). Reaction with allyl isocyanate followed by ring opening and then reaction with mercuric acetate affords the mercury derivative (45) as the acetate rather than the hydroxide as above. Reaction with sodium chloride converts that acetate to the halide (46). Displacement on mercury with the disodium salt of thioglycollic acid affords the diuretic mercaptomerine (47). ... 

Further routes of cyclizations have been studied in parallel in the case of cis- and rra/J5-2-hydroxymethyl-l-cyclohexylamine (106) (880PP73). The preparation of thiourea or urea adducts 107 and 108 with phenyl isothiocyanate or phenyl isocyanate proceeds smoothly. The reaction of 107 with methyl iodide and subsequent alkali treatment, by elimination of methyl mercaptan, resulted in the iminooxazine 109 in high yields. The ring closures of both cis and trans thiourea adducts to 1,3-oxazines proceed with retention. Cyclodesulfuration of the adduct 107 by mercury(II) oxide or N,N -dicyclohexylcarbodiimide resulted in the iminooxazine 109, but the yield was low and the purification of the product was cumbersome. The ring closure of 108 with thionyl chloride led to the iminooxazine 109 in only moderate yield. 

The most extensively investigated 1,2-diazocines are 3,4,5,6,7,8-hexahydro derivatives, of interest in connection with studies on the properties of cyclic azo compounds. These compounds are obtained from the hydrazines (159) usually not isolated, by oxidation with yellow mercury(II) oxide. 3,8-Diaryloctahydrodiazocines are prepared by reduction of the azines dialkyl and unsubstituted derivatives are obtained by hydrolysis of the N,N-bis(ethoxycarbonyl) compounds (69JA3226,70JA4922). Cyclization of 2,7-diaminooctane with IFs gave the 3,3,8,8-tetramethyl compound (78CB596). 

Mercury(II) oxide and acetic acid effect the cyclization of l,4-diaryloxybut-2-ynes to 4-aryloxymethylchromenes. The transformation was attributed to cyclization of the butanone which resulted from hydration of the alkyne (72JHC489). However, it has since been shown that similar butanones do not cyclize to chromenes under the cyclization conditions (78JOC3856). Instead, a mechanism is proposed which involves a charge-induced Claisen rearrangement which is triggered by 7r-complex formation between the metal ion... 

Treatment of isothiocyanate 2 with nicotinoyl hydrazide in boiling 1,4-dioxane afforded 84 in 85% yield this cyclized on treatment with yellow mercury(II) oxide in ethanol67,69 to oxadiazole 85. The mass spectrum of, and H-n.m.r. data for, 85 were also reported.68 Interestingly, in this case, the cyclization of 84 occurred preferentially, with the formation of the 1,3,4-oxadiazole derivative 85, in contrast to literature70 detailing similar... 

Iodine-Mercury(II) oxide, 149 a-METHYLENE ALDEHYDES AND KETONES 1,4-Diazabicyclo[2.2.2]octane, 92 Dimethyl sulfoxide, 124 Formaldehyde, 136 Methoxyallene, 177 Methylene cycloalkanes By cyclization reactions Diacetatobis(triphenylphos-phine)palladium(II), 91 l-Hydroxy-3-trimethylsilylmethyl-3-butene, 147... 

Successive intramolecular oxypalladation of dihydroxyalkynes has been used for the synthesis of spirocyclic and bridged acetals. Equations (78) to (80) show the syntheses of some insect pheromones by this method.198 The results from several diols suggest that preferred modes for initial cyclization are 5-endo > 5-exo > 6-endo. A related conversion of 8-hydroxyoct-4-ynoic acid to an oxaspirolactone with mercury(II) oxide has been reported.199... 

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