Dimethyl copper lithium

The monobromide(s) 146 were treated under strong basic conditions at elevated temperature, slowly generating the y-lactone 147 by ring opening, and consecutive Sn2 reaction in 87% yield (Scheme 14). The isopropyl group was introduced in a four-step sequence. Claisen condensation with methyl formate led to a mixture of the enol and the enol ether, which by treatment with diazomethane, yielded in 80% the enol ether, 148. To introduce the methyl groups, the enol ether was converted into the thioenol ether. 1,4-Addition of dimethyl copper lithium afforded the... 

Denethylammopyndine (DMAP) 361.433 Dimethyl copper lithium 260 DimethyHormamlde DMF 211,229... 

For the sake of comparison, the regio- and stereo-selectivity of some nucleophilic openings of vinyl-oxiranes with organometallic reagents derived from copper, lithium, sodium and other metals indicate the control avail le under some conditions. Complete control of diastereoselectivity in the opening of cyclic vinyloxiranes is available, for example by utilizing palladium(0)-catalyzed conditions in the reaction of die sodium salt of dimethyl malonate with cyclic vinyloxiranes.Increased substitution on the vinyl portion of the vinyloxirane leads to isomerization with opening, as in the case of the disub-stituted vinyloxirane (150 equation 49). ... 

Chlorocarbonyl-2-methoxy-5-methylpyrazine with lithium dimethyl copper reagent in ether gave 3-acetyl-2-methoxy-5-methylpyrazine 2-acetyl-3-methoxy-pyrazine and 2-acetyl-3,6-dimethoxy-5-methylpyrazine were prepared similarly (844), but 2-chlorocarbonyl-3-methoxy-5-methylpyrazine with lithium dimethyl copper in ether gave a mixture of 2-acetyl-3-methoxy-5-methylpyrazine and 2-(l-hydroxy-1-methylethyl)-3-methoxy-5-methylpyrazine (844). 

A reinvestigation of the adducts formed by addition of difluorocarbene to 17j5-acetoxy-17a-ethynyl-3-methoxyoestra-l,3,5(10)-triene has confirmed the structure of the major product as (529) and led to a revision of the structure assigned to a diadduct byproduct to (530). Formation of this latter compound and its geometric isomer, which was also isolated, involves a novel acetyl migration. Lithium dimethyl copper converts the main difluorocarbene adduct (529) into the diene (532) in high yield. 

Lithium dimethyl copper reacted with (186) to introduce a methyl group stereo-selectively trans to the 5-isopropyl group. The enolate anion (187) so formed underwent intramolecular alkylation to give the cis-decalone(188), which was reduced to d/-valerane (189). Conjugate addition of lithium methyl vinyl cuprate to cyclopent-2-... 

On the other hand, treatment of lithium dimethyl copper with some a,3-epoxy ketones failed to yield any alkylated product. 

Treatment of 3,4,6-tri-O-acetyl-l, 2-anhydro-D-glucose with dimethyl- or diphenyl-copper lithium gave. 

Stannane 6a underwent facile transmetalation in tetrahydrofuran at — 78 °C on treatment with butyllithium to afford 6b. Addition of the lithium reagent 6b to a solution of 1.1 equivalents of copper(I) bromide-dimethyl sulfide in 1 1 diisopropyl sulfide/tetrahydrofuran at — 78 °C gave the copper reagent 6c, which reacted with methyl vinyl ketone at —78 "C in the presence of boron trifluoride-diethyl ether65, producing 7 in 55% yield65. 

Organobis(cupratesY, spiroannelation.16 1,4-Dilithiobutane, prepared from 1,4-dichlorobutane and lithium in ether at 0°, on reaction with copper thiophenoxide (2 equiv.) forms a biscuprate, formulated as 1 for convenience. This dimetallic reagent adds to 3-halo-5,5-dimethyl-2-cyclohexenones (2) to form the spiro-[4.5]decanone 3 in yields as high as 96%. Cuprates prepared from other Cu(I) sources are less efficient, as is the cuprate prepared from di-Grignard reagents... 

The beneficial effect of added phosphine on the chemo- and stereoselectivity of the Sn2 substitution of propargyl oxiranes is demonstrated in the reaction of substrate 27 with lithium dimethylcyanocuprate in diethyl ether (Scheme 2.9). In the absence of the phosphine ligand, reduction of the substrate prevailed and attempts to shift the product ratio in favor of 29 by addition of methyl iodide (which should alkylate the presumable intermediate 24 [8k]) had almost no effect. In contrast, the desired substitution product 29 was formed with good chemo- and anti-stereoselectivity when tri-n-butylphosphine was present in the reaction mixture [25, 31]. Interestingly, this effect is strongly solvent dependent, since a complex product mixture was formed when THF was used instead of diethyl ether. With sulfur-containing copper sources such as copper bromide-dimethyl sulfide complex or copper 2-thiophenecarboxylate, however, addition of the phosphine caused the opposite effect, i.e. exclusive formation of the reduced allene 28. Hence the course and outcome of the SN2 substitution show a rather complex dependence on the reaction partners and conditions, which needs to be further elucidated. 

Calcium acetylide, 0585 Copper(II) acetylide, 0615 Copper(I) benzene-l,4-bis(ethynide), 3236 Copper l,3,5-octatrien-7-ynide, 2933 DicopperQ acetylide, 0619 DicopperQ 1,5-hexadiynide, 2165 Dimethyl(phenylethynyl)thallium, 3298 Dimethyl-1-propynylthallium, 1938 GoldQ acetylide, 0573 Lithium acetylide, 0992 Lithium bromoacetylide, 0580 Lithium chloroacetylide, 0599 Lithium 1-heptynide, 2834... 

Olivetol. 3,5-Dimethoxybenzyl alcohol. (This can be made by reducing 3,5-dimethoxybenzoic acid, or it can be purchased.) (10 g) in 100 ml of methylene chloride is cooled to 0° and 15 g of PBrs is added. Warm to room temp and stir for 1 hour, then add a little ice water followed by more methylene chloride. Add petroleum ether to precipitate the benzyl bromide, which is separated off. 9.3 g of the benzyl bromide is put in a flask with 800 ml of dry ether and then add 15 g of copper iodine at 0°. Add butyl lithium (16% in hexane) and stir for four hours at 0°. Add saturated NH4CI and extract with ether. The ether is removed by evaporating in vacuo to give the olivetol dimethyl ether which must be demethylated by one of the methods given in the above formulas. Yield A little over 4 g. Taken from HCA, 52, 1132. 

Since sodium borohydride usually does not reduce the nitrile function it may be used for selective reductions of conjugated double bonds in oc,/l-un-saturated nitriles in fair to good yields [7069,1070]. In addition some special reagents were found effective for reducing carbon-carbon double bonds preferentially copper hydride prepared from cuprous bromide and sodium bis(2-methoxyethoxy)aluminum hydride [7766], magnesium in methanol [7767], zinc and zinc chloride in ethanol or isopropyl alcohol [7765], and triethylam-monium formate in dimethyl formamide [317]. Lithium aluminum hydride reduced 1-cyanocyclohexene at —15° to cyclohexanecarboxaldehyde and under normal conditions to aminomethylcyclohexane, both in 60% yields [777]. 

---