Organoalkalis additions

In addition to the decreased polarizability of the heavier metals, their larger radii require higher metal coordination numbers to achieve steric saturation. As a result, extensive aggregation, frequently coinciding with rather limited solubility in non-donor solvents, and occasionally even in donor solvents, complicates the characterization of these species in solution and the solid state. In fact, several structural characterizations of organoalkali species have relied on recent advances in powder diffraction techniques using synchrotron radiation.1 ... 

This represented the discovery of the first addition of an organometallic (organoalkali) compound to a C=C double bond. The organopotassium compound used had at that time been known for only 4 years. It was found by the author and Schnell (46) as the result of a systematic search for the simplest ether to be split by an alkali metal according to the equation... 

This is an excellent reaction for the conversion of most halides to acids containing one additional carbon atom. Carbonation of Grignard reagents and organoalkali compounds gives acids in yields of 50-85%. Ether solutions of the organometallic compounds formerly were treated with carbon dioxide gas at 10° to -10°. A more recent technique involves pouring the solution onto excess crushed Dry Ice. Carbon dioxide... 

The compositions RjPbM are deduced by conversion to benzyltriorganoleads on addition of benzylchloride to RjPbM solns . They are complexes "" of a diorgano-lead(II) compound with an organoalkali metal derivative, analogous to alkali halo-plumbates(II). 

In addition, the organoalkali initiators only work effectively with the conjugated monomers. They are ineffective with the olefins, or even with ethylene. (Some success has been reported (A8) in the polymerization of ethylene to a reasonably high molecular weight in highly chelated organolithium systems. However, these polymerizations required relatively higher temperatures and showed much evidence of termination reactions.)... 

Some other contributions of organometallic compounds to fundamental research are (a) the detection of free alkyl radicals by the pyrolysis of lead alkyls (b) the classification of hydrocarbon acidity via organoalkali compounds (c) the study of Lewis acid-base interactions with Group III alkyls (d) the development of the concept of electron-deficient compounds by the study of metal alkyls (e) the discovery of stereospecific olefin polymerization and (f) the investigation of nucleophilic additions to unsaturated organic compounds via reactive metal alkyls. 

Addition of sp3 organoalkali compounds to isocyanates and isothiocyanates have been reported incidentally. 

Reactions of organoalkali compounds with disulfides and trialkylchlorosilane are often extremely fast. The usual procedure involves addition of the reagents to a... 

Chain Transfer Reactions Chain transfer reactions to polymeric organoalkali compounds can occur from solvents, monomers, and additives that have p/f values lower than or similar to those of the conjugate acid of the carbanionic chain end [3]. Relatively few monomers that undergo anionic polymerization exhibit chain transfer to monomer. Chain transfer has been well documented for the anionic polymerization of 1,3-cyclohexadiene. The chain transfer constant was calculated to be 2.9 x 10 at... 

Highly nucleophilic organoalkali metal reagents are widely utilized in organic synthesis [7, 8]. The reaction with an electrophile provides a new bond that is a fundamental bond forming reaction. In this type of reaction, function of alkali metal as Lewis acid affects the reactivity and reaction selectivity. Recent extensive studies on mechanism have revealed that the mixed aggregation of substrate, alkali metal reagent, solvent, and additives control the reaction. 

There are several reasons why it may be advantageous to switch from an organoalkali into the generally less reaetive organomagnesium intermediate. Due to its electrophilicity, the magnesium reagent may exert push-pull control over the addition of allylmetals onto oxiranes. This is a key step, for example, in the synthesis of natural Sabina ketone 16 (Seheme 1-12). ... 

Organomagnesiums frequently prove superior also in other types of reactions. They may facilitate the oxidation of a carbon-metal to a carbon-oxygen bond, secure clean monoaddition of an acetylide to an activated ester (a critical issue in a monensin synthesis X favor in the presence of a copper catalyst 1,4-addition onto a conjugated enone over 1,2-addition, reorient the attack of formaldehyde on a benzylic entitiy from the a- to the or /to-position, and provide diastereoselectivity in nucleophilic additions onto aldehydes. Furthermore organomagnesiums combine under carbon-carbon linking with a variety of organic halides, tosylates, and acetates if the process is mediated by transition elements such as palladium(O) copper(I), nickel(II) or iron(II) Organoalkalis are often less fit to enter such catalytic cycles. 

In the aromatic and heterocyclic series, no hydroboration is possible. In general, an organoalkali intermediate is prepared by metalation or halogen/metal permutation before being treated with a boric acid derivative such as trimethyl borate or, because of its cleaner reaction, triisopropyl borate. The resulting ate complex sets free the oxidizable boronate upon addition of water or a stoichiometric amount of diluted hydrochloric acid. The boronate can be accessed directly when fluorodimethoxyborane is used instead of a boric acid ester as the adduct eliminates lithium fluoride spontaneously. The oxidation relies on the same procedures and principles as outlined above. 

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