Lithium perchlorate-/dichloromethane

A similar stereospecific conjugate addition to epoxysulfone 323 was also observed416. When this reaction of 323 was carried out with methyllithium at — 78 °C dichloromethane-diethyl ether (1 1) in the presence of lithium perchlorate, compounds 324 and 325 were obtained in a ratio of 95 5. On the other hand, in the treatment of 323... 

Catalysis by lithium perchlorate in dichloromethane Diels-Alder reactions and 1,3-Claisen rearrangements [100]... 

In the Mukaiyama aldol additions of trimethyl-(l-phenyl-propenyloxy)-silane to give benzaldehyde and cinnamaldehyde catalyzed by 7 mol% supported scandium catalyst, a 1 1 mixture of diastereomers was obtained. Again, the dendritic catalyst could be recycled easily without any loss in performance. The scandium cross-linked dendritic material appeared to be an efficient catalyst for the Diels-Alder reaction between methyl vinyl ketone and cyclopentadiene. The Diels-Alder adduct was formed in dichloromethane at 0°C in 79% yield with an endo/exo ratio of 85 15. The material was also used as a Friedel-Crafts acylation catalyst (contain-ing7mol% scandium) for the formation of / -methoxyacetophenone (in a 73% yield) from anisole, acetic acid anhydride, and lithium perchlorate at 50°C in nitromethane. 

U. Schmid and H. Waldmann, Synthesis of fucosyl saccharides under neutral conditions in solutions of lithium perchlorate in dichloromethane, Chem. Eur. J., 4 (1998) 494-501. 

Good results were also obtained with lithium perchlorate in dichloromethane and diethyl ether. It has been shown that the lithium cation acts as a Lewis acid and the effects are not due to an internal pressure [80]. The acceleration is much more pronounced for hetero Diels-Alder reactions as compared to the allcarbon cycloadditions. With chiral aldehydes a high level of chelation control has been observed (see later) [81,82]. 

If the reactions are carried out in a nitrile as solvent, rather than dichloromethane, using triflic acid as catalyst, a modified Ritter reaction takes place, and the intermediate nitrilium ion traps the liberated amine, forming an amidine (Scheme 67). In an earlier reaction cf. Scheme 67) the lithium perchlorate catalyzed reaction of sulfenyl chlorides with alkenes in the presence of nitriles had also given l-amido-2-sulfenyl adducts. Ritter products are also obtained in good yields by anodic oxidation (Pt or C, 1.2-1.4 V) of disulfides in acetonitrile, in the presence of excess alkene, using B114NBF4 as supporting electrolyte (Scheme 68). ... 

Cycloaddition of enantiomerically pure l-methoxy-3-sulfmyl-l,3-butadiene 1 to methyl acrylate (2) in the presence of a suspension of lithium perchlorate in dichloromethane proceeds with complete regioselectivity affording adducts 3 and 4 in 70 % yield with an cndoiexo ratio of 100 0 and d.r. [(17 ,2/t)/(lS, 25)] 96 421. 

Methoxyphenyl n-pentyl ketone was formed in 85% yield by the addition of a mixture of anisole and caproic anhydride in dichloromethane to a suspension of lithium perchlorate (1 mole) and a small proportion of antimony pentachloride (allowed first to stir together for 1 hour) in dichloromethane, followed by refluxing for 30 mins., and work-up by quenching with aqueous sodium bicarbonate (ref. 124). 

As to acceleration of the isomerization, addition of salts such as lithium perchlorate in acetonitrile solution and tetrabutylammonium tetrafluoro-borate in dichloromethane in DCA-sensitized irradiation of cis-stilbene enhanced the isomerization. A salt effect is probably responsible for retardation of recombination between the resulting stilbene radical cations and counteranions (DCA--, etc.) [143, 146]. 

In another article [29], lower contact angle values were reported for PTh and PPy films electropolymerized in dichloromethane. SEM study showed that PPy films were smooth and densely packed while PTh films showed a relatively porous and fibroid sfructure. Contact angle value of 51° was obtained for thick films of PPy electropolymerized in a lithium perchlorate aqueous medium [30]. This highlights the differences in wettability when changing one or several condihons. 

Pleiadiene has been prepared by ring-expansion of (43), using a two-step procedure. Treatment of (43) with n-butyl-lithium and dichloromethane gave a mixture of bicyclobutane (44) and pleiadiene (total yield 68 %). Thermolysis, irradiation, treatment with silver perchlorate in benzene, and treatment with iodine in CCl (preferred) were all then used to convert this mixture into pleiadiene exclusively (60-80%). "... 

Cyclization of enone (9) in hexane with boron trifluorideetherate in presence of 1,2-ethanedithiol, followed by hydrolysis with mercury (II) chloride in acetonitrile, yielded the cis-isomer (10) (16%) and transisomer (11) (28%). Reduction of (10) with lithium aluminium hydride in tetrahydrofuran followed by acetylation with acetic anhydride and pyridine gave two epimeric acetates (12) (32%) and (13) (52%) whose configuration was determined by NMR spectroscopy. Oxidation of (12) with Jones reagent afforded ketone (14) which was converted to the a, 3-unsaturated ketone (15) by bromination with pyridinium tribromide in dichloromethane followed by dehydrobromination with lithium carbonate and lithium bromide in dimethylformamide. Ketone (15), on catalytic hydrogenation with Pd-C in the presence of perchloric acid, produced compound (16) (72%) and (14) (17%). The compound (16) was converted to alcohol (17) by reduction with lithium aluminium hydride. 

Polythiophene is readily produced by inserting a working electrode, counterelectrode, and reference electrode into a nonaqueous electrolyte in which 0.1 to 1.0 M thiophene is dissolved and then increasing the cell potential to greater than 1.6 V (versus SCE). Salts such as lithium or tetrabutylammonium perchlorate, hexafluo-rophosphate, or trifluoromethylsulfonate are typical electrolytes. Acetonitrile, ben-zonitrile, dichloromethane, and tetrahydrofuran are suitable solvents. As previously discussed for polypyrrole, polythiophene has been prepared in aqueous solutions [247]. A conductive, electroactive poly thiophene film was polymerized from a phosphoric acid-water-thiophene system using mild electrochemical polymerization conditions. 

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