Bis acetal

Chemical Name 2,2 -[ ([4-[(Aminocarbonyl)amino] phenyl] arsinidene] bis(thio)] bis (acetic acid]... 

Alkenes can also be oxidized with metallic acetates such as lead tetraacetate or thallium(III) acetate " to give bis-acetates of glycols. Oxidizing agents such as benzoquinone, Mn02, or 02, along with palladium acetate, have been used to convert conjugated dienes to l,4-diacetoxy-2-alkenes (1,4 addition). ... 

The interesting work of Martin and coworkers " on oxygen-substituted sul-furanes(VI) lO-S-4 and 12-S-6 species made available for the first time quasi mono-and bis-acetals of sulfones (1 and 2). Proton-catalyzed fragmentation of lb led to the sulfone isomer 3 the corresponding fragmentation of 2a gave, depending on reaction conditions, the isomeric sulfone 4 or a mixture of the sulfone isomers 4 and 5 . 

Maybe the best well-estabhshed method for the preparation of Bfxs is the oxidative ring closure of o-nitroanihne derivatives. AlkaUne hypochlorite, NaOCl/KOH, has been the most commonly used reagent but electrochemical synthesis [17] and bis(acetate-0-)phenyUodine as oxidizer have also been employed [18]. The procedure is particularly useful where the other... 

Just as certain pyranose sugars can give rise to bis-acetal or bis-ketal derivatives which constitute linearly fused 5 6 6 systems (cf. Section 12.17.2.1.7), another set of bis-acetals and bis-ketals - in many cases derived from the same sugars - correspond to angularly fused 5 6 6 systems. These, like their linearly fused analogues, serve to protect, selectively, four hydroxyl groups of the parent sugars, and cyclic carbonates (l,3-dioxolan-2-ones) may fulfill similar functions. 

The location of protons in intermolecularly hydrogen-bonded carboxylate-carboxylic acid complexes, for example sodium hydrogen bis(acetate) [1],... 

Bis(acetic acid)trifluoroborane, 4 144t Bisacetoacetarylide, pigment for plastics, 7 366t... 

The reaction of 2-fluoro-2,2-dinitroethanol (119) with divinylether (118) under different conditions gives three products, namely, the expected vinyl acetal (120) and the bis-acetal (121) from addition of one and two equivalents of 2-fluoro-2,2-dinitroethanol, respectively, and the vinyl ether (122), which results from franx-etherification of (118) with loss of acetaldehyde. Shackelford and co-workers found that by altering the nature of the Lewis acid catalyst and the reaction stoichiometry they were able to alter the distribution ratio of these products. 

Attempts to make C2-symmetric ferrocenes by double lithiation of a bis-acetal met with only limited success . A second lithiation of the ferrocenylacetal 298 leads to functionalization of the lower ring of the ferrocene, in contrast with the second adjacent lithiation of the oxazolines described below. This can be used to advantage if, for example, the first-formed aldehyde 301 is protected in situ by addition of the lithiopiperazine 53 °, directing f-BuLi to the lower ring (Scheme 139) °. The same strategy can be used to introduce further functionalization to products related to 302. For example, silane 303, produced in enantiomerically pure form by the method of Scheme 138, may be converted to the ferrocenophane 304 by lithiopiperazine protection, lithiation and functionalization (Scheme 140) . 

Die Kondensation des in situ aus seinem Bis-acetal freigesetzten 5-Amino-nonandials mit 3-Oxo-pentandisaure-dimethylester bei pH 5,5 fuhrt unter dreifachem RingschluB zu 1,3-Dimethoxycarbonyl-2-oxo-perhydro-9b-aza-phenalen, das sich zu 2-Oxo-perhydro-9b-aza-phenalen dealkoxycarbonylieren laBt5 (s.S. 1092) ... 

The stoichiometric equivalents of halofluorides have been recently applied to transform alkylene dithioacetals into gcm-difluorides.70-71 Dithioacetals such as 1,3-dithiolanes and 1,3-dithianes arc readily obtained from the corresponding carbonyl compounds by the reaction with ethane-1,2-dithiol or propane-1,3-dithiol in the presence of the complexes boron trifluoride-bis(acetic acid) or boron trifluoride-diethyl ether. Using a two-step procedure, a range of aldehydes and ketones can be converted into gem-difluorides under mild conditions. 

A novel synthesis of the sesquiterpene ( )-cinnamodial (148) utilizes the furan ring as a latent 1,4-dialdehyde synthon (81JA3226). The triol (141) was thus oxidized to the ketofuran (142). Oxidation of the furan moiety with lead tetraacetate afforded a 90% yield of epimeric diacetates (143) which when exposed briefly to DBU gave dienone (144). Epoxidation of (144) and exposure of the epoxide (145) to p-toluenesulfonic acid gave the bis-acetal (146). Reduction of this intermediate to a diol and hydrolysis of the bis-acetal furnished dialdehyde (147). Acetylation of the secondary hydroxyl group completed the synthesis of cinnamodial (Scheme 32). 

Maleic thioanhydride and its dichloro derivative function as dienophiles. Cycloaddition with cyclopentadiene and butadiene has been reported (Scheme 155) (72AHC(14)33l). Succinic thioanhydride undergoes bis-Wittig condensations (Scheme 156) the product from ethoxycarbonylmethylenetriphenylphosphorane aromatizes to the thiophene-2,5-bis-acetic ester (454) (75LA1967). 

Cation radical cyclization can be performed (and accelerated significantly) under sonication. Thus, the reaction of methyl vanillate with phenyliodonium bis(acetate) is initiated by ultrasonic irradiation and gives rise to the corresponding oquinone monoketal, which is trapped by a series of furanes. Monoadducts are formed reactions can be conducted at room temperature and are essentially complete within 15-50 min (Avalos et al. 2000). 

In the second step meto-chloroperbenzoic acid (MCPBA) epoxidizes the resulting bis-acetal from the /J-face. The weak 0-0 bond of MCPBA undergoes attack by electron rich substrates like alkenes. This reaction is syn stereospecific and believed to take place via transition state 48.30... 

Acetals of /9-keto aldehydes are hydrolyzed in acid media and hence under these conditions they give pyrazoles just as the ketoaldehydes themselves.297-300 Recently the bis-acetal of malondialdehyde has been used extensively for the synthesis of pyrazoles unsubstituted on the ring carbon atoms the reaction yields single products since the bis-acetal is symmetrical.217,271,273,301-307 Cyclization takes place in... 

Ley and co-workers studied the applicability of immobilized phenyliodine(III) bis]acetate) as an oxidative coupling reagent in an effort to develop orchestrated multistep syntheses using... 

The formal synthesis of ( )-catharanthine by Imanishi et al.l09a consists in a new preparation of the pentacyclic ketoamide (269), which has previously been converted into catharanthine by Biichi et a/.123 The critical stage in this synthesis (Scheme 38) was the preparation of the quinuclidine ketone (270) by an intramolecular aldol reaction on the keto-aldehyde derived from the piperidine bis-acetal (271). 

Conagenin (39) is a promising anticancer natural product isolated in 1991 from the culture broths of Streptomyces roseosporus20 (Scheme 4.1n). The chelation-controlled Zn(B 114)2 reduction of the p-hydroxy ketone 40 produced the 1,3-syn-diol 41 in 30 1 diastereoselectivity. Protection of the hydroxyl groups gave the bis-acetate 42, which was then subjected to oxidative cleavage to afford the acid 43. 

Treatment with one equivalent of an acyl chloride agent is no good because the primary hydroxyl group is more reactive instead, the chemists acetylated both hydroxyl groups, and then treated the bis-acetate with mildly basic methanol (K2CO3, MeOH, 20°C), which reacted only at the less hindered acetoxy group and gave the desired compound in 65% yield. 

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