Lithium triethylcarboxide

A. Lithium triethylcarboxide (Solution 1). A thoroughly dried, 1-1., three-necked, round-bottomed flask is fitted with a septum inlet with serum cap, a reflux condenser, and a magnetic stirrer. The flask is purged with and maintained under an atmosphere of dry nitrogen. A solution of 300 ml. of 1.66 M butyllithium (0.50 mole) in hexane (Note 1) is introduced into the flask by syringe (Note 2) and cooled to 0° in an ice bath. Then 58 g. (0.50 mole) of 3-ethyl-3-pentanol (Note 3) is added slowly but constantly by syringe (Note 4). At the end of addition the yellow tint of the butyllithium solution disappears. The alkoxide solution is standardized by hydrolysis of aliquots in water and by titration of the resulting lithium hydroxide with standard acid to a phenol-phthalein end point (Note 5). 

Alternatively, if only one use of the solution of lithium triethylcarboxide (1) is planned, the required amounts of butyllithium solution and 3-ethyl-3-pentanol may be reacted, and the resulting solution of lithium triethylcarboxide used without standardization. 

Lithium triethylcarboxide (1) is the base of choice for these conversions. The use of less hindered alkoxide or amide bases results in poorer yields. In this procedure 1.5-2.0 equivalents of base are required, although with more bulky alkyl groups attached to boron only 1 equivalent is necessary. The use of the more hindered 2,6-diisopropylphenol to form the borinic ester gives a 96% yield of the bicyclic ketone with only 1 equivalent of base however, in the work-up procedure this phenol is more difficult to separate from the ketone. 

Lithium triethylcarboxide 3-Pentanol, 3-ethyl-, lithium salt (8,9), (32777-93-8). 

Chiral ketones.3 Asymmetric hydroboration of a prochiral alkene with monoisocampheylborane followed by a second hydroboration of a nonprochiral alkene provides a chiral mixed trialkylborane. This product reacts with acetaldehyde with elimination of a-pinene to give a chiral borinic acid ester in 73-100% ee. Treatment of this intermediate with a,a-dichloromethyl methyl ether (2,120 5, 200-203) and lithium triethylcarboxide followed by oxidation results in an optically active ketone in 60-90% ee. 

Brown ei al. now find that tri-/i-butylcarbinol is obtained in essentially quantitative yield by the reaction of tri-n-butylborane with chlorodifluoromethane (or other tri-substituted methanes) under the influence of lithium triethylcarboxide (equation 2). 

The new method has the advantage that the reaction proceeds rapidly at 65°, a temperature at which isomerization of organoboranes is not significant. Various alkoxides were examined hindered alkoxides provided the best results. Of these lithium triethylcarboxide proved superior to potassium r-butoxidc and potassium triethylcarboxide. Chlorodifluoromethane can be replaced by chloroform, in which case the yield is somewhat lower (85%) but the procedure is somewhat more convenient. 

TETRALONES Methylene chloride. nilADIAZlRIDINE 1,1-DIOXIDES Sodium hydride-t-Butyl hypochlorite. THIOAMIDES Thioacetamide. TRIALKYLCARBINOLS Carbon monoxide. Lithium triethylcarboxide. TRIAZOLES Ethyl azidofomate. Sodium azide. 

DABCO). 1,5-Diazabicy do [5,4,0 ] undec-ene-5 (DBU). Diethylamine. Ethylene-diamine. Lithio propylidene-f-buty limine. Lithium bis(trimethylsilyl)amide. Lithium f-butoxide. Lithium diethylamide. Lithium diisopropylamide. Lithium N-isopro-pylcyclohexylamide. Lithium orthophosphate. Lithium 2,2,6,6-tetramethylpiper-ide. Lithium triethylcarboxide. 1,2,2,6,6-Pentamethylpiperidine. Piperazine. Potassium f-butoxide. Potassium hexamethyldi-silaznae. Potassium hydride. Potassium hydroxide. Pyridine. 4-Pyrrolidopyridine. Quinuclidine. Sodium ethoxide. Sodium methoxide. Sodium thioethoxide. Tetra-methylguanidine. Thallous ethoxide. Tri-ethylamine. 

THIOAMIDES Thioacetamide. TRIALKYLCARBINOLS Carbon monoxide. Lithium triethylcarboxide. TRIAZOLES Ethyl azidoformate. Sodium azide. 

Lithium triethylcarboxide Trialkylcarbinols from boranes s. 27, 892 with a,a-dichloromethyl ether instead of chlorodifluoromethane s. J. Org. Chem. 38, 2422, 3968 (1973). 

C-H functionalization. A few conditions for the C-H functionalization of pyridazine have emerged in the last decade. The Ca-position is predominantly functionalized. A C4-regioselective C-H arylation of pyridazine is achieved using a copper catalytic system (copper iodide/phenanthroline, 1 1 ratio) in combination with hindered lithium triethylcarboxide in DMF (eq 11). The arylation occurs at the most acidic position of pyridazine. 

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