Lithium hydroperoxide

In addition to the high levels of asymmetric induction, two other attractive features of this sequence of reactions warrant comment. First, both acylation and hydrolysis of the chiral auxiliary are facile, high yield reactions. Second, we have recently found that the lithium hydroperoxide hydrolysis protocol described in Part C is the method of choice for the deaoylation process. This reagent exhibits remarkable regioselectivity for attack at the desired exocyclic acyl carbonyl moiety. ... 

Lanthanum nitrate, analysis of anhydrous, 5 41 Lead (IV) acetate, 1 47 Lead(II) 0,0 -diethyl dithiophos-phate, 6 142 Lead (IV) oxide, 1 45 Lead(II) thiocyanate, 1 85 Lithium amide, 2 135 Lithium carbonate, formation of, from lithium hydroperoxide 1-hydrate, 5 3 purification of, 1 1 Lithium chloride, anhydrous, 6 154 Lithium hydroperoxide 1-hydrate, 5 1... 

Lithium hydroxide 1-hydrate, formation of, from lithium hydroperoxide 1-hydrate, 6 3 Lithium nitride, 4 1 Lithium oxide, 6 1, 5 Lithium peroxide, 5 1... 

In both cases, only one diastereomer could be detected using high-temperature H NMR spectroscopy. Removal of the oxazolidinone auxiliary from compounds (S,S)-101 and (/ ,R)-101 by treatment with lithium hydroperoxide followed by acidification and treatment with diazomethane generated the corresponding methyl esters (S)-102 and (/ )-102 which have opposite configuration at C2. Amination of either... 

In the total synthesis of (+)-trienomycins A and F, Smith et al. used an Evans aldol reaction technology to construct a 1,3-diol functional group8 (Scheme 2.1i). Asymmetric aldol reaction of the boron enolate of 14 with methacrolein afforded exclusively the desired xyn-diastereomer (17) in high yield. Silylation, hydrolysis using the lithium hydroperoxide protocol, preparation of Weinreb amide mediated by carbonyldiimidazole (CDI), and DIBAL-H reduction cleanly gave the aldehyde 18. Allylboration via the Brown protocol9 (see Chapter 3) then yielded a 12.5 1 mixture of diastereomers, which was purified to provide the alcohol desired (19) in 88% yield. Desilylation and acetonide formation furnished the diene 20, which contained a C9-C14 subunit of the TBS ether of (+)-trienomycinol. 

Base-catalysed hydrolysis using alkali metal hydroxides or carbonates in aqueous methanol or THF remains the commonest method for cleaving simple esters limited mainly by the stability of the substrate to the basic conditions. In more complex substrates, lithium hydroxide in a mixture of THF-methanol-P O (2 2 1) is the base of choice.1-3 In a synthesis of Lepicidin A, Evans and Black4 accomplished the hydrolysis of a methyl ester with lithium hydroxide in aqueous /err-butyl alcohol at 35 °C [Scheme 6.1). Destannylation that accompanied hydrolysis with other solvents was not observed nor was harm inflicted on the TIPS and TES ethers. In a synthesis of cydoisodityrosine derivatives, Boger and co-workers attempted to hydrolyse methyl ester 2 1 [Scheme 6.2] with 1-3 equivalents of lithium hydroxide in a mixture of THF-methanol-HaO (3 1 1) at room temperature, but the desired hydrolysis was accompanied by scission of the tripeptide side chain from the ring system. However, when the reaction was conducted in the presence of the more nucleophilic lithium hydroperoxide, the desired hydrolysis was achieved in 97% yield without racemisation. 

Whereas the saponification of the a-azidocarboximides proceeds in high yields, the hydrolysis of the sterically demanding (S)-7 (R = -Bu), however, proved to be problematic, since cleavage occurs predominantly at the endocyclic oxazolidinone carbonyl. A dramatic improvement has been achieved in the lithium hydroperoxide mediated hydrolysis of this substrate. The desired cnantiomerically pure a-azido acid (S)-8 (R = r-Bu) is thereby obtained in 98 % yield along with a 98% recovery of the chiral auxiliary. 

R)- and (25)-2-Azidoalkanecarboxylic Acids 8 by Lithium Hydroperoxide Mediated Hydrolysis of 7 General Procedure2 ... 

This hydrolysis of the chiral imide auxiliary in the presence of other potentially vulnerable ester groups has proved to be very successful. A lucid example is given in the synthesis of the cyclic tripeptide OF4949-III 14. The complex a-azidocarboximide 11 is transformed into the corresponding a-azido acid 12 by means of lithium hydroperoxide in 89% yield. 

Conversion to the Acid. Hydroxide and peroxide agents saponify acyl imides in excellent yields however, with ster-ically hindered acyl groups endocyclic cleavage may predominate upon treatment with Lithium Hydroxide. Lithium Hydroperoxide, however, is highly selective for the exocyclic carbonyl moiety. 

Although this problem can be overcome by using lithium hydroperoxide, the use of this reagent on large scale can be hazardous. In order to completely circumvent this problem, Davies... 

Evans, D. A., Britton, T. C., Ellman, J. A. Contrasteric carboximide hydrolysis with lithium hydroperoxide. Tetrahedron Lett. 1987, 28, 6141-6144. 

Morzycki, J.W., Gryszkiewicz, A., and Jastrzebska. I., Neighboring group participation in epoxide ring cleavage in reactions of some 16a,17a-oxidosteroids with lithium hydroperoxide. Tetrahedron, 57, 2185, 2001. 

O-Dechloroacetylation of IV.61 by treatment with thiomea gave IV.62, which was subsequently reprotected as the hydrogenolyzable 4-methoxybenzyl ether with 4-methoxybenzyl trichloroacetimidate and triflic acid under phase transfer catalysis conditions [104]. Saponification of the benzoate and methyl esters with lithium hydroperoxide followed by methanolic sodium hydroxide and acidification then gave the acid IV.63. O-Sulfonation of IV.63 was achieved with the sulfur trioxide-tri-methylamine complex to give the disulfate IV.64 as the sodium salt. Finally, hydro-genolysis of IV.64 with Pd/C in aqueous methanol afforded the target disaccharide IV.51. 

LITHIUM HYDROPEROXIDE 1-HYDRATE, LITHIUM PEROXIDE, AND LITHIUM OXIDE... 

Lithium hydroperoxide 1-hydrate is a white, crystalline compound, which belongs to the orthorhombic system (o = 7.92 A., b = 9.52 A., c — 3.20 A.).4 The calculated density with four molecules to the unit cell is 1.60.4 The measured density is 1.69. Additional water may be trapped mechanically to give compositions slightly above the 1-hydrate.4 The compound reacts spontaneously with atmospheric carbon dioxide to form lithium carbonate and release oxygen. It decomposes gradually on standing in a closed system at room temperature to lithium hydroxide 1-hydrate. 

Lithium hydroperoxide 1-hydrate (part A) is placed in a vacuum desiccator over phosphorus (V) oxide, and the pressure is reduced to about 20 mm. After standing for 18 days at room temperature under these conditions, the material is converted quantitatively to 96% (or better) lithium peroxide. The anhydrous peroxide can be preserved indefinitely in a dark bottle under refrigeration. Anal. Calcd. for Li202 Li20, 65.0 peroxide O, 34.9. Found Li20, 64.5 peroxide O, 34.0. 

See also Lithium hydroperoxide 1-hydrate, lithium peroxide, and lithium oxide, synthesis 1... 

LiCl Lithium chloride, 6 154 LiN Lithium nitride, 4 1 LiNH2 Lithium amide, 2 135 Li0H-H20 Lithium hydroxide, 5 3 Li02HH20 Lithium hydroperoxide 1-hydrate, 5 1, 2, 4 Li2C03 Lithium carbonate, 1 1 5 3... 

In 1989 Oppolzer reported that the enolates of A-acyl sultams derived from camphor afford highly diastereoselective alkylation products with a variety of electrophiles including those which are not allylically activated [88]. The sultam is deprotonated using either butyllithium with a catalytic amount of cyclohexyl isopropyl amine, or butyllithium alone, or sodium hexamethyldisilyl amide.As illustrated in Scheme 3.18, alkylation occurs selectively from the Re face of the Z(( )-enolate to give monoalkylated sultams which can be cleaved by LAH reduction or lithium hydroperoxide catalyzed hydrolysis. Representative examples are listed in Table 3.7. 

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