Lithium-aluminum / manganese dioxide

Lithium-aluminum / manganese dioxide (LiAl/MnOj) LiAl MnOj LiAsFg, EC/BC/DME Polypropylene LiAl + Mn02 Li MnOj + Lii, Al... 

TABLE 34.19 Rechaigeable Lithium Aluminum/Manganese Dioxide Coin-Type Batteries... 

Rearrangements Aluminum bromide. Calcium carbonate. Dimethylthiocarbamyl chloride Dimsylsodium. 1,3-Dithiane. Lithium diethylamide. Manganese dioxide. Methyl vinyl ketone, 4a —> 5a. Michler s ketone. Norbornene. Perchloric acid. Pinacol-type see Potassium /-butoxide. Potassium /-butoxide. Silver perchlorate. Thallium triacetate. Triethyloxonium-fluoroborate. 

Lithium aluminum hydride Manganese dioxide Hydrazine hydrate... 

Several total syntheses of antirhine (11) and 18,19-dihydroantirhine (14) have been developed during the last decade. Wenkert et al. (136) employed a facile route to ( )-18,19-dihydroantirhine, using lactone 196 as a key building block. Base-catalyzed condensation of methyl 4-methylnicotinate (193) with methyl oxalate, followed by hydrolysis, oxidative decarboxylation with alkaline hydrogen peroxide, and final esterification, resulted in methyl 4-(methoxycar-bonylmethyl)nicotinate (194). Condensation of 194 with acetaldehyde and subsequent reduction afforded nicotinic ester derivative 195, which was reduced with lithium aluminum hydride, and the diol product obtained was oxidized with manganese dioxide to yield the desired lactone 196. Alkylation of 196 with tryptophyl bromide (197) resulted in a pyridinium salt whose catalytic reduction... 

Magnesium methyl carbonate, 310 Malic acid, 135 Malyngolide, 224, 316 Manganese(II) chloride-lithium aluminum hydride, 310 Manganese dioxide, 311 Manicone, 121... 

Figure 19.1 Synthetic scheme for example pheromone components. Abbreviations al and a2 = Wittig-Homer condensations with triethyl 2-phosphonopropionate and triethyl 2-phosphonobutyrate, respectively b = reduction of ester with lithium aluminum hydride c = partial oxidation of alcohol with manganese dioxide to aldehyde dl and d2 = Wittig condensations with ethyltriphenylphosphonium bromide and propyltriphenylphosphonium bromide, respectively e = condensation with dimethylhydrazone phosphonate reagent f = hydrolysis under acidic conditions. Compound numbers are as in Table 19.1.

Protopine alkaloids. A notably efficient route to protopanes is the photooxygenation (Rose Bengal or Methylene Blue) of an enamine such as 1 to give an amido ketone (2), which can be converted into 3 by reduction with lithium aluminum hydride in THF followed by oxidation with activated manganese dioxide. The overall yield is about 65%. 

J-Oisubstitated SH-indoks. 3,3-Disubstituted 311-indoles (3) can be prepared readily by lithium aluminum hydride [or sodium bis-(2-mcthoxyethoxy)aluminum hydride, 3, 260-261 this volume] reduction of 3,3-disubstituted oxindoles (1), followed by oxidation of the indoline (2) with activated manganese dioxide or potassium permanganate in acetone. 

Two asymmetric synthesis approaches to chiral cyclopentenone derivatives can be envisaged. The first, reduced to practice by Noyori (43), involved reduction of cyclopentene-l,4-dione with lithium aluminum hydride chirally modified with binaphthol to give R-4-hydroxycyclopent-2-en-l-one in 94% e.e. Alternatively, manganese dioxide oxidation of allylic alcohol [40] (Fig. 7), in analogy to the cis isomer (54), would be expected to give the same enone. 

Reductive removal of the bromo groups of 28 with lithium aluminum hydride followed by oxidation of the formed triasteranol with manganese dioxide gave triasteranone in 60% overall yield. 

When tazettinol and isotazettinol were reduced with lithium aluminum hydride and the resultant diols were treated with acid, the ethers, deoxytazettinol (CLIII) and deoxyisotazettinol (CLIV), respectively, were formed. Both deoxytazettinols gave deoxytazettinone (CLV) with manganese dioxide. 

The cis relationship between the phenyl and methoxyl groups in CLIX has been confirmed by recent synthetic studies of Uyeo and his co-workers (86). Dihydroisotazettinol (in which the 3-hydroxyl and the phenyl are trans) was oxidized by manganese dioxide to CLIXa. Treatment of CLIXa with lithium aluminum hydride and cyclization of the resultant triol with dilute sulfuric acid gave an ether (CLIXb), the methi-odide of which afforded the neutral compound CLIXc upon Emde reduction. The synthesis of CLIXc started with CLIXd, the condensation product of piperonyl cyanide and methyl acrylate. Dieckmann... 

Thus, reduction of androst-5-ene-l,17-dione (1-5) with lithium aluminum hydride reduced both 3- and 17-carbonyl groups, that at Cn cleanly to the /8-epimer and the ketone at C3 to a mixture of epimers (3-1) (Scheme 5.3). Treatment of the mixture of epimers with manganese dioxide oxidizes the allylic alcohol at C3, leaving that at C17 untouched, affording testosterone (3-2). 

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