Initiators, organolithium

Addition of Grignard reagents and organolithium compounds to the pyridazine ring proceeds as a nucleophilic attack at one of the electron-deficient positions to give initially... 

The mechanism of organolithium addition to naphthyl oxazolines is believed to occur via initial complexation of the alkyllithium reagent to the oxazoline nitrogen atom and the methyl ether to form chelated intermediate 17. Addition of the alkyl group to the arena 7t-system affords azaenolate 18, which undergoes reaction with an electrophile on the opposite face of the alkyl group to provide the observed product 4. The chelating methyl... 

When chiral additives such as ( —)-sparteine has added to the initial reaction with the organolithium reagent, quenching with CO2 produces carboxylic acids with good asymmetric induction. 

By modification of method A, Jones has transformed 2,4-bis-OBoc-benzy-aldehyde 5 into the 3-carbomethoxy dihydrocoumarin 43 in 68% yield (Fig. 4.23).lla The reaction proceeds by the addition of phenyl Grignard followed by addition of a preformed mixture of methyl malonate and sodium hydride and warming to room temperature. This particular example obviates the need for prior initiation by an organolithium reagent. 

During addition of an ethereal solution of deuterium oxide (containing some peroxide) to a suspension of the organolithium reagent in pentane, a violent explosion occurred. This may have been initiated by the peroxide present, but probably... 

More recently, a number of different copolymer structures have been prepared from butadiene and styrene, using modified organolithiums as polymerization initiators ( 4). Organolithium initiated polymerizations have gained prominence because stereo-control is combined with excellent polymerization rates, and the absence of a chain termination reaction facilitates control of molecular weights and molecular weight distributions ( 5). 

SN, reactions of primary stabilized organolithium compounds on polyalkylmethacrylates affords a very versatile synthetic route to model ketonic copolymers substitution is selective and quantitative up to DSm of 0.60,and it is easily monitored by the initial... 

The alkyllithium-initiated, anionic polymerization of vinyl and diene monomers can often be performed without the incursion of spontaneous termination or chain transfer reactions (1). The non-terminating nature of these reactions has provided methods for the synthesis of polymers with predictable molecular weights and narrow molecular weight distributions (2). In addition, these polymerizations generate polymer chains with stable, carbanionic chain ends which, in principle, can be converted into a diverse array of functional end groups using the rich and varied chemistry of organolithium compounds (3). 

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