Lithium acylation

For most methoxycarbene complexes a one pot modification of the above method is utilized. This involves direct alkylation of the initially formed lithium acylate carbene complex with trifluoromethanesulfonate or with methyl fluorosulfonate. The method is successfully employed for preparation of chromium140 as well as molybdenum and tungsten monocyclic uation 65), bicyclic (equation 66) and tricyclic carbene complexes... 

Alkyl (or phenyl) lithium formed with iron pentacarbonyl in situ lithium acyl-tetracarbonyl ferrates, Li[RCOFe(CO)4], which with iodonium salts afforded aryl ketones (48-85%) [41]. 

Lithium acylates are readily transformed to the substantially more thermally stable tetramethylaimnonium acylates by... 

More complex alkoxy substituents may be introduced by an acylation-alcoholysis sequence (Scheme 2), [3] Typically, this method involves the conversion of the lithium acyl metalate into the tetramethylammonium salt 5 which upon low-temperature acylation affords the thermolabile acyloxycarbene... 

Syntheses with lithium acyl carbonyl metalates Ketones from halides... 

M lates s. Lithium acyl carbonyl metalates Metalation (s. a. Ring metalation)... 

There are a wide variety of methods for introduction of substituents at C3. Since this is the preferred site for electrophilic substitution, direct alkylation and acylation procedures are often effective. Even mild electrophiles such as alkenes with EW substituents can react at the 3-position of the indole ring. Techniques for preparation of 3-lithioindoles, usually by halogen-metal exchange, have been developed and this provides access not only to the lithium reagents but also to other organometallic reagents derived from them. The 3-position is also reactive toward electrophilic mercuration. 

MPD-1 fibers may be obtained by the polymeriza tion of isophthaloyl chloride and y -phenylenediamine in dimethyl acetamide with 5% lithium chloride. The reactants must be very carefully dried since the presence of water would upset the stoichiometry and lead to low molecular weight products. Temperatures in the range of 0 to —40° C are desirable to avoid such side reactions as transamidation by the amide solvent and acylation of y -phenylenediamine by the amide solvent. Both reactions would lead to an imbalance in the stoichiometry and result in forming low molecular weight polymer. Fibers are dry spun direcdy from solution. 

Ethynodiol diacetate (53) is prepared by reduction of the 3-oxo group of norethindrone (28) with lithium tributoxyalurninum hydride, followed by acylation with acetic anhydride-pyridine (78,79). It has been reported that higher yields can be obtained in the reduction step by using triethylanainoalurninum hydride (80). 

Side-chain lithiation with lithium diisopropylamide and subsequent alkylation or acylation is a practical method for the preparation of various alkyl-, alkenyl- and acyl-methyl-pyridazines 78CPB2428, 78CPB3633, 79CPB916) (Scheme 47). 

Birch reduction of indole with lithium metal in THF in the presence of trimethylsilyl chloride followed by oxidation with p-benzoquinone gave l,4-bis(trimethylsilyl)indoIe (106). This is readily converted in two steps into l-acetyl-4-trimethylsilylindole. Friedel-Crafts acylation of the latter compound in the presence of aluminum chloride yields the corresponding 4-acylindole (107) (82CC636). 

Acyl-4-aminoisoxazoles have been prepared by cyclization of a-(acylmethoxy-imino)nitriles in the presence of lithium hydroxide (equation 44) (80LA1623). 

The synthesis of 3-acyl- and 3-aroyl-l,2-benzisoxazoles was accomplished by the desulfurization of (562). The dithioacetal (562) was prepared by the addition of the lithium salt of propenedithioacetal to an isocyanate with subsequent base cyclization (equation 61) (B-79MI41609). 

These reactions are presumed to occur through aroyl triflate intermediates which dissociate to aiyl acylium ions. Lithium perchlorate and scandium triflate also promote acylation. ... 

The preparation of enamines by reduction of aromatic heterocyclic bases and their quaternary salts or of lactams is not the most useful approach (97). The lithium aluminum hydride reduction of N-acyl enamines has been used with both fruitful and unsuccessful results. A series of 3-N-acetyl -d -cholestenes (104) has been prepared by desulfurization of the appropriate thiazolidine (105) (98,99). Lithium aluminum hydride reduction of the... 

N-acyl enaminc (104, R = CHjCHj) gave an unstable enamine (106) which decomposed readily to 3-cholestanone. The steroidal N-acetyl enamines (107 and 108, R = C HjCHj) can be reduced by lithium aluminum hydride in tctrahydrofuran to the corresponding enamines (109, R = CJH5CH2) in 90 and 68% yield, respectively 100). Attempts to reduce the enamide (107, R = CH3) led to the formation of the impure enamine (109, R = CHj), which decomposed to the hydroxy ketone (110). 

The Rosenmund reduction is usually applied for the conversion of a carboxylic acid into the corresponding aldehyde via the acyl chloride. Alternatively a carboxylic acid may be reduced with lithium aluminum hydride to the alcohol, which in turn may then be oxidized to the aldehyde. Both routes require the preparation of an intermediate product and each route may have its advantages over the other, depending on substrate structure. 

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