Dimethylcopper lithium

Problem 19.23 How might you use IR spectroscopy to determine whether reaction between 2-cyclo-hexenone and lithium dimethylcopper gives the direct addition product or the con-1 jugate addition product ... 

Use of 3-trimethylsilylbut-3-en-2-one in conjugate addition/annelation reaction with 2-methylcyclohexenone after conjugate addition with lithium dimethylcopper. 

Lithium bis(trimethylsilyl)cuprate, 29, 52 Lithium diaikylamides, 100 Lithium l-(dimethylamino)naphthalenide (LDMAN), 68, 69. 77 Lithium dimethylcopper, 131 Lithium hexamethyldisilazide, 73. 78 Lithium t-octyl-t-butylamide, 100 2.6-Lutidine, 93.94... 

The reaction with alkyl- and aryllithium reagents has also been carried out without preliminary formation of RLi a mixture of RX and the carbonyl compound was added to a suspension of lithium pieces in THF.364 Yields were generally satisfactory. The magnesium analog of this process is called the Barbier reaction,365 Lithium dimethylcopper Me2CuLi... 

Compound 2 was then transformed into the conjugated enone 161. Lithium dimethylcopper 1,4-addition on enone 161 and reaction of the resulting enolate with dibenzoyl peroxide gave compound 162 in good yield. Reaction of 162 with methylmagnesium iodide at low temperatures furnished compound 163 again in good yield. Thus by this sequence, an excellent control of... 

Regioselective ring opening of the epoxide in 200 occurs in the presence of bromine and triphenylphosphine to give the bromohydrin 201 (R = Br), which on treatment with azobisisobutyronitrile (AIBN) and tributyltin hydride gives the c o-6-hydroxy-2-azabicyclohexane 201 (R = H) <2001JOC1811>. The 5-substituted derivatives of alcohol 201 (R = Me or Ph) are obtained by treatment of 200 with lithium dimethylcopper or lithium diphenylcopper <20040L1669>. 

Methoxy-a-tetralone (137), which on formylation at room temperature followed by treatment with n-butanethiol in presence of p-toluenesulfonic acid gave the compound (138), which was converted with lithium dimethylcopper and acetic anhydride to (139). Subjection of (139) to dehydrogenation, hydrolysis and methylation, respectively, yielded (140) which was converted to tetralone (141) by reduction, hydrolysis and methylation of pyralidine enamine. Alkylation of (141) with 2-... 

Methylcopper is less reactive than lithium dimethylcopper towards acid halides (295), but the yield of methyl ketones can be increased by performing the reaction in hexamethylphosphorus triamide (HMPT) or CHgCN (224). 

Imidazole acid halides are very reactive and are easily converted into other acid derivatives <82JHC56l, 84JOC1951>. They cannot, however, be used as precursors of acetyl functions in reaction with lithium dimethylcopper <92JHCl02i>. 

Corey and Posner8 have prepared lithium di-n-butylcopper and lithium diethyl-copper and used them for cross coupling in the same way. In general they are more reactive but also less stable thermally. They also tend to induce halogen-copper exchange more than lithium dimethylcopper, but this side reaction can be reduced by addition to the reaction mixture of an excess of the alkyl halide corresponding to the n-alkylcopper reagent. Yields of 60-80% were obtained. 

Dimethylcopperlithiuin (Lithium dimethylcopper) (CH3)2CuLi [1, 277, before l,2-Dimethyl-4,5-di(mercaptomethyl)benzene]. Mol. wt. 100.55. 

The structure and absolute stereochemistry of hinesol (282) has now been firmly established by an unequivocal synthesis which involved the tricyclic dienone (329) prepared from 6-methoxy-l-tetralone. Treatment of the dienone with lithium dimethylcopper gave a mixture of syn and anti enones (330). By a series of stereoselective reactions this compound was converted to the diol (331) whose mono-mesylate underwent a base-induced cleavage to give the spiro[4,5]-ketone (332). Elaboration of this ketone to hinesol was accomplished along... 

Steroid chemists will be interested in the application of lithium dimethylcopper for epoxide opening, to give trans-2-methylcyclohexanols lithium diphenylcopper similarly introduces a phenyl substituent. The reagent is said to be superior to either the Grignard reagent or alkyl-lithium for this purpose, and is selective for epoxides even in the presence of oxo-groups. 

A related route via enol phosphates provides some rather inaccessible olefins. The 4-methyl-3-ene (333), for example, is obtained by reducing a 4-en-3-one with lithium-ammonia, esterifying the resulting lithium A -enolate (334) with diethyl phosphorochloridate [(EtO)2PCl], and reducing the enol phosphate (335) with lithium. 5/ -Methylation of a 4-en-3-one with lithium dimethylcopper, with in situ conversion of the lithium A -enolate into its phosphate, followed by reduction, similarly afforded the 5 -methyl-3-ene (336). Use of lithium enolates prevents isomerisation of enolate anions, which is likely with other metal salts. ° ... 

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