Acylation of organometallic compounds

Acylation of Organometallic Compounds and Heteroatom-Stabilized Carbanions With Carboxylic Acid (Derivative)s Synthesis of Ketones... 

Fig. 6.50. Acylation of organometallic compounds with various Weinreb amides (A, D and E) of carbonic acid.

Yu. A. Ol dekop and N. A. Maier, Synthesis of Organometallic Compounds by Decarboxylation of Metal Acylates. Science and Technology, Minsk, 1976. 

The Conversion of Organometallic Compounds to Ketones, Aldehydes, Carboxylic Esters, or Amides Acyl-de-metallation, etc. 

In Section 6.5 you learned that the acylations of hydride donors or of organometallic compounds, which give aldehydes or ketones, often are followed by an unavoidable second reaction the addition of the hydride or organometallic compound to the aldehyde or the ketone. In this chapter, we will study the intentional execution of such addition reactions. 

First, coordinatively unsaturated active palladium catalyst, PdL2, is produced via dissociation of the ligands, which then reacts with acyl halide to give the acylpalladium intermediate. Since deinsertion of CO of the acylpalladium derivatives may occur simul-taneously, the next step, transmetallation (so-called metathesis), is the most crucial for the efficiency of the overall reaction. A variety of organometallic compounds, such as boron, aluminum, copper, zinc, mercury, silicon, tin, lead, zirconium, and bismuth, are used as the partner in this coupling reaction without loss of CO. In this section, the important features of the cross-coupling reactions of a variety of organometallic compounds with acyl halides and related electrophiles are discussed. 

Palladium-catalyzed coupling reactions of organozinc compounds with acyl halides are the fastest and mildest among the known methods using a variety of organometallic compounds. 

Palladium- and nickel-catalysed aryl- and acyl-demetallation of organometallic compounds, N.A. Bumagin, A.B. Ponomaryor and I.P. Beletskaya,... 

The chemistry of fluorinated 1,3,5-triazines is not as well studied as the chemistry of their chloro derivatives. In case of fluorotriazines the reactions directed on the ring nitrogen atoms, displacement of fluorine atoms and reactions on carbon atoms on the ring with retention of the fluorine atoms appear to be the most characteristic ones. In this section the N-alkylation and N-acylation reactions, as well as replacement of fluorine atoms by a variety of nucleophiles will be considered. Metallation of fluorotriazines and synthesis on the basis of organometallic compounds, as well as the cross-coupling reactions were described. Also several examples of photochemical reactions and transformations are presented. 

The carbonyl group of acid derivatives reacts with the nucleophilic carbanion available from organo-metallic reagents. However, the reactions of the individual classes of compounds are not as straightforward as the addition reactions of organometallic compounds with aldehydes and ketones. Addition of a carbanion to the acyl carbon atom generates a tetrahedral intermediate that can decompose to give a ketone that will react further with another equivalent of the carbanion. 

The same resolution can be efficiently carried out on structurally more complex compounds that are optically active for the helical structure of the molecule, i.e., bis(hydroxymethyl) thiaetherohelicene [160]. In this way, a nearly optically pure helical molecule can be obtained (Scheme 33). This method has been successfully applied also to resolution of organometallic compounds and a few interesting results are shown in Scheme 34. Tiicarbonyl [(ir (6)-cycloheptatriene)chromium(0)] and ferrocenyl alcohols have been examined as substrates of the lipase-catalyzed acylation, and the reaction can be accomplished in a highly enantioselective manner [161,162]. 

Similarly, 1-alkylpyrroles, indoles, furans, thiophenes [60], a-picoline [61], enols, malonates [76], and organometallic compounds [56, 62] react with acyl imines of trifluoropyruvates to give derivatives of a-trifluoromethyl a-amino acids... 

Phthalic anhydride also shows the ability to inhibit thermal destruction of polyolefins [21]. Among the organometallic compounds may be quoted organotin compounds R2Sr(OR )2, where R2 means alkyl, aryl, or cycloalkyl OR means alkoxyl, acyl, or R2Sn(CH2COORi)2, where Rj—Ci—Cm means alkyl, allyl, or benzyl Ro represents chloro-, mono-, or triorga-notin mercaptans [22,23]. 

The Conversion of Acyl Halides to Ketones With Organometallic Compounds ... 

Halogenation of alkenyl organometallic compounds Addition of hydrogen halides to triple bonds Halogenation of alkynes or allenes Addition of alkyl halides to triple bonds Addition of acyl halides to triple bonds... 

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