Methoxy methyllithium

The completion of the synthesis of the polyol glycoside subunit 7 requires construction of the fully substituted stereocenter at C-10 and a stereocontrolled dihydroxylation of the C3-C4 geminally-disub-stituted olefin (see Scheme 10). The action of methyllithium on Af-methoxy-Af-methylamide 50) furnishes a methyl ketone which is subsequently converted into intermediate 10 through oxidative removal of the /j-methoxybenzyl protecting group with DDQ. Intermediate 10 is produced in an overall yield of 83 % from 50) , and is a suitable substrate for an a-chelation-controlled carbonyl addition reaction.18 When intermediate 10 is exposed to three equivalents of... 

Boronic esters, RB(OR )2 react with methoxy(phenylthio)methyllithium, LiCH(OMe)SPh, to give salts, which, after treatment with HgCl2, and then H2O2, yield aldehydes.This synthesis has been made enantioseiective, with high ee values (>99%), by the use of an optically pure boronic ester, for example ... 

Addition of the arylamines 117 to 2-methoxy-3-methyl-l,4-benzoquinone 118 affords regioselectively the 5-arylamino-2-methoxy-3-methyl-l,4-benzo-quinones 119 (Scheme 37). Palladium(II)-catalyzed oxidative cyclization leads to the carbazole-l,4-quinones 28 [135,136],previously obtained by the iron-mediated approach (cf. Scheme 14). Regioselective addition of methyllithium to the quinones 28 provides carbazomycin G 29a and carbazomycin H 29b [96,135]. Reduction of 29a with lithium aluminum hydride followed by elimination of water on workup generates carbazomycin B 23a [135]. Addition of heptylmag-... 

Hibino et al. reported the total synthesis of carbazomycin G (269) by the regioselective addition of methyllithium onto 3-methoxy-2-methylcarbazole-l,4-quinone (941) (653). The required immediate precursor of carbazomycin G, carbazole-l,4-quinone 941, was obtained from 3-(2-methoxyethenyl)-N-(phenylsul-fonyDindole (986). The benzannulation involves an allene-mediated electrocyclic reaction of a 67t-electron system generated from the 2-propargylindole 989, which was derived from the 3-vinylindole 986 in three steps. 

An efficient process for one-carbon homologation to aldehydes is based on cyclic boronate esters.17 These can be prepared by hydroboration of an alkene with dibromobor-ane, followed by conversion of the dibromoborane to the cyclic ester. The homologation step is carried out by addition of methoxy(phenylthio)methyllithium to the boronate ester. The migration step is induced by mercuric ion. Use of enantioenriched boranes and boronates leads to products containing the groups of retained configuration.18... 

Methoxy(phenylthio)trimethylsilyl-methyllithium, 182 l-Methoxy-3-phenylthio-3-trimethyl-silyl-l-propenyl-3-lithium, 182 1 -Methoxy-4-(trimethylsilyl)-1 -butene-3-ynyl-2-lithium, 180 Methyllithium, 142, 188, 203, 214, 315 Methyllithium-Methylaluminum bis-(2,6-di-t-butyl-4-methylphenoxide), 203... 

Methoxy(trimethylsilyl)methyllithium, 331 (E)-l-Methoxy-3-trimethylsilyloxy-l,3-butadiene, 332-334 Methyl 2-acety[aerylate, 334-335 Methyl acrylate, 7-8, 22, 50 Methylal, 193... 

This is an addition-elimination reaction of methyllithium with iV-methyl-iV-methoxypropionamide forming 2-butanone. As illustrated below using arrow pushing, methyllithium initially adds to the amide. Unlike the process illustrated in Problem 6(f), a second methyllithium does not add and an alcohol is not formed. This is explained by the ability of lithium to coordinate between the two present oxygen atoms. The first is the oxygen of the former carbonyl and the second is the oxygen associated with the methoxy component of the illustrated amide. Due to the stability of this type of five-membered interaction, initial... 

Methoxy(phenylsulfanyl)(trimethylsilyl)methyllithium 324 has been used as acyllithium and, depending on the electrophile and the deprotection conditions, it can transfer the acyltrimethylsilyl, the methoxycarbonyl or the (phenylsulfanyl)carbonyl group. By alkylation of intermediate 324 with primary alkyl iodides, bromides and chlorides in the presence of HMPA, followed by oxidation of compound 325 with NaI04, acylsilanes... 

The acylation of methoxy(phenylsulfonyl)methyllithium 340 has only been performed with an ester to provide in 86% yield the corresponding / -kcto sulfone used for the synthesis of rapamacin517. 

Aldehydes Alkyidimesitylborane. Chloro-methyltrimethylsilane. Diethyl[(2-tetrahy-dropyranyloxy)methylphosphonate. N,N-Dimethylchloromethyleniminum chloride. Dimelhyl(methylthio)sulfonium tetrafluom-borate. Methoxy(phenylthio)methyllithium. Methylthiomethyl p-tolyl sulfone. 1-Phen-ylthio-1 -trimethylsilylethylene. Tetrakis-(Iriphcnylphosphine)palladium. Thexyl-chloroborane-Dimethyl sulfide. 

Boronic esters RB(OR )2 react with methoxy(phenylthio)methyllithium LiCH(OMe)SPh to give salts, which, after treatment with HgCl2, and then H2O2,... 

The synthesis of cytovaricin passes through several highly functionalized intermediates including compound (13). Glycosidation of the alcohol at C-3 was carried out with the N-methoxy-N-methyl-amide functionality in place. The addition of methyllithium and deprotection of the alcohol completes the formation of ketone (14) without competing epimerization or elimination (equation 6). 

By way of comparison, a very similar transformation has been accomplished without the use of the N-methoxy-A -methylamide. Hydrolysis of methyl ester (19) affords the corresponding carboxylic acid which was treated directly with methyllithium to afford a 70% overall yield of methyl ketone. ... 

Methoxy(phenylthio)methane and methoxy(phenylsulfonyl)methane are useful formyl anion equivalents for one-carbon homologation. For instance, addition of methoxy(phenylthio)methyllithium to ketones, followed by rearrangement of the adduct, provides a new method for the preparation of a-(phe-nylthio) aldehydes (equation 39). The reanangement is stereospecilic. This method has been used for the total synthesis of annelated furans such as (-)-)-euryfiiran, butenolides such as isodenninin and con-fertifolin and spirocyclic tetrahydiofurans and butenolides. ... 

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