Lithium N-isopropylcyclohexylamid

A number of other methods exist for the a halogenation of carboxylic acids or their derivatives.134 The acids or their chlorides or anhydrides can be a chlorinated by treatment with CuCl in polar inert solvents (e.g., sulfolane).135 Acyl halides can be a brominated or chlorinated by use of N-bromo- or N-chlorosuccinimide and HBr or HC1.136 The latter is an ionic, not a free-radical halogenation (see 4-2). Direct iodination of carboxylic acids has been achieved with L-Cu(II) acetate in HO Ac.137 Acyl chlorides can be a iodinated with L and a trace of HI.138 Carboxylic esters can be a halogenated by conversion to their enolate ions with lithium N-isopropylcyclohexylamide in THF and treatment of this solution at - 78° with I2138 or with a carbon tetrahalide.139 Carboxylic acids, esters, and amides have been a fluorinated at -78°C with F2 diluted in Ni.,4°... 

Lithium diisopropylamide, 257 Lithium hexamethyldisilazide, 257 Lithium hydride, 165 Lithium N-isopropylcyclohexylamide-Hexamethylphosphoric triamide, 227 Mercuration, 174 by other metals... 

In a 1971 paper, Rathke and Lindert reported that lithium N-isopropylcyclohexylamide (LICA) is a superior reagent for the generation of ester enolates. Subsequent workers, however, have found that LDA works just as well. This base has the added virtue of being derived from a relatively volatile amine (the b.p. of diisopropylamine is 84 C). 

The O-protected and unprotected ( )-crotyl lactates 5a-d require longer enolate generation times and higher temperatures for the rearrangement486. Best conditions for the rearrangement of the benzyl ether 5b involves deprotonation with lithium N-isopropylcyclohexylamide in tetrahydrofuran at —78 °C followed 30 minutes later by chlorotrimethylsilane and slow warming to reflux. 

Claisen rearrangement of ally silyl ethers (4,307-308). Katzenellenbogen and Christy have extended the rearrangement of silyl enol ether derivatives of allylic acetates to y,S-unsaturated acids to systems in which a trisubstituted double bond is generated. Thus 3-acetoxy-2-methyl-l-nonene (1) was treated with lithium N-isopropylcyclohexylamide (LilCA) in THF at -78° and then with f-butyldimethylchlorosilane to give the f-butyldimethylsiloxyvinyl ether... 

Other activated sulfoxides. This alkylative elimination reaction has been extended by Trost and Bridges to a one-pot synthesis of alkenes, vinyl sulfides, a, l-unsaturated sulfoxides, and a,j3-unsaturated nitriles. The sulfoxides (1-4) are converted into the anions by lithium N-isopropylcyclohexylamide or sodium hydride and are then alkylated at 20° in THE or DME elimination is then effected by raising the temperature to reflux. In some cases trimethyl phosphite is added as a scavenger for phenylsulfenic acid. Typical results are formulated in the equations. The elimination reaction is facilitated by an aryl, thioaryl, or... 

Dienic carboxylic acids. Prater has described a method for addition of an isoprene unit to an allylic alcohol. The method is iUustrated for the conversion of the ester (1) of geraniol into farnesenic acid (3). The ester is treated with lithium N-isopropylcyclohexylamide (LilCA, 4, 306-309) and then with trimethylchlorosilane. The resulting trimethylsilylketene acetal (a) undergoes... 

Lithium N-isopropylcyclohexylamide, 79, 238, 255, 394, 627 Lithium isopropylmercaptide, 343 Lithium methoxyaluminum hydride, 341-342... 

Lithium(3,3-dimethyl-l-butynyl)-l,l-di-ethoxy-2-piopenyl cuprate, 300 Lithium dimethyl cuprate, 301-302 Lithium di-n-octylcuprate, 356 Lithium diphenylphosphide, 302 Lithium (fl-(E)-propenyl cuprate, 302-303 Lithium divinyl cuprate, 190 Lithium-Ethylamine, 284-286, 472 Lithium fluoride, 244 Lithium hexamethyidisilazide, 337 Lithium B-isopinocampheyl-9-borabi-cycloj 3.3.1) -nonyl hydride, 303 Lithium N-isopropylcyclohexylamide, 169 Lithium o-lithiobenzylate, 67 Lithium (l-lithiopropionate, 303 Lithium methyl mercaptide, 303-304 Lithium methylthioformaldinc, 305 Lithium naphthalenide, 303, 305-306 Lithium perchlorate, 212 Lithium n-propylmercaptide, 283 Lithium selenophenolate, 306-307 Lithium 2,2,6,6-tetramethylpiperidide, 299, 307-308... 

Bromination of a polyunsaturated carboxylic acid. Bromination of an acid of this type by the method of Rathke and Lindert (4, 306) proved unsatisfactory owing to low yields, but was accomplished by conversion of 1 into the a-anion with lithium N-isopropylcyclohexylamide, bromination with diethyl dibromomalonate at — 78°, and removal of the ester group. The pure acid 3 is fairly stable. ... 

Lithium N-isopropylcyclohexylamide Carboxylic acid esters from halides Synthesis with addition of 2 C-atoms Modified malonic ester synthesis... 

Lithium N-isopropylcyclohexylamide O-Silyl O-alkyl keteneacetals from carboxylic acid esters... 

Org Synth (1943) Coll Vol 2 268 Lithium N-isopropylcyclohexylamide Tetr Lett (1971) 2953... 

The chemistry of preformed enolates emerged in temporal and causal coherence vith the EDA area . Although lithium and magnesium salts of diisopropylamine vere first developed in the nineteen-fifties [40], lithium diisopropylamide (EDA) has been a videly used reagent since 1970, because of its behavior as a soluble, strong, and non-nucleophilic base [14]. EDA and related bases, for example lithium hexamethyldisilazane (LIHMDS) [41], lithium N-isopropylcyclohexylamide (LICA) [42], and lithium 2,2,6,6-... 

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