Palladium catalysis acylation

The mechanism of propene/CO copolymerisation by palladium catalysis is essentially analogous to those of ethene and styrene (i. e., chain propagation proceeds via alternating insertions of CO into Pd-alkyl and alkene into Pd-acyl controlled by p-chelates) [1]. 

The EMCR has been extended from obtaining enantiomerically pure alcohols to obtaining such amines. Prochiral ketoximes were transformed to optically active amine acetates in a coupled CALB/palladium catalysis in the presence of an acyl donor at 1 atm hydrogen (Figure 18.15) (Choi, 2001). 

The more reactive lithium dialkenylcuprates (R2CuLi) cannot be directly acylated even at low temperature, because further addition to the product takes place. These reagents can be modified in situ so that the actual species undergoing reaction is an organozinc (requires palladium catalysis) however, other methods for generating organozincs are available that do not involve prior organocopper formation (Section 1.13.4.4). Stoichiometric vinylcopper and other copper-mediated acylations were not directly applicable to the case shown in equation (58) (however, see Section 1.13.2.1). 

The acylation of the mildly nucleophilic organostarmanes was first reported by Migita in 1977 through the use of palladium catalysis. However, the reported conditions were harsh and of limited... 

Amino acid synthons can be prepared from iodoalanine with no loss of optical integrity (Scheme 48). The amino acid was transformed into a novel zinc reagent through reductive metallation with a zinc-copper couple in benzene/dimethyl acetamide. This organometallic was acylated under palladium catalysis in good overall yield. ... 

The scope of vinyl metals as sources of nucleophilic vinyl groups is very great. As well as the expected electrophiles such as halogens, alkyl and acyl halides, aldehydes and ketones, unsaturated carbonyl compounds and epoxides, they also combine with aryl and alkenyl halides with palladium catalysis. The usual stereochemical course is retention at the vinyl group. It is necessary to decide whether the vinyl metal is reactive enough or whether it must first be transformed into an ate complex. Since most of these vinyl metals can be converted into each other with retention, this is an unusually versatile group of reagents. 

Allenyl ketones presynthesised, or generated in situ by acylation of silyl-allenes, or by palladium(0)-catalysed isomerisation of conjugated or non-conjugated alkynyl ketones, can be cyclised to furans. The ring closure has been effected with silver or palladium catalysis acylation of silylallenes leads to the furan directly. In the presence of water, palladium(II)-catalysed closure of / ,7-alkynyl ketones is believed to proceed via the enol, not the allene. l,2,3-Trienyl-4-ols have also been shown to cyclise to give furans. ... 

B.ii.e Carbonylation and Acylation. The keto function in pyrrolo[3,2-c]pyridin-4-ones and pyrido[3,4- ]pyrrolizidin-l-ones can be enolized and triflated to yield the substrates 72 and 73, respectively (Scheme 34). Replacement of the triflyloxy group by carbonylation is effected with palladium catalysis. Reaction of the pyrido[3,4-fc]-pyrrolizidin-l-ones 73 was complicated by formation of a by-product, namely, the 2-methoxy adduct 74. In the latter case competitive palladium-assisted elimination of the triflyloxy group leads to an imminium intermediate, which adds a methoxy group as a... 

There have been several reports of ortho-acylations using palladium catalysis. Orthoacylation of acetanilides with aldehydes is catalysed by palladium trifluoroacetate in the presence of f-butylhydroperoxide. A likely pathway involves the formation of a cyclopalladated intermediate (57), which reacts with an acyl radical to give (58) followed by carbon—carbon bond formation through reductive elimination. A similar methodology has been used in the preparation of a range of ort/io-acylacetanilides. ... 

Interestingly, only BiBrj gave quantitative yields of the products 416, while other bismuth(III) halides and Bi(OTf)3 had absolutely no effect for the reported transformation. The aUcenylbismuth derivatives could also be trapped in sUu with iodine or coupled with acyl chlorides in the presence of a palladium catalyst [119]. Addition of organogold compoimds to activated carbon-carbon triple bonds has also been reported to proceed under palladium catalysis [120]. Thus, (PhjPljPdClj or Pd2(dba)j complexes successfully promoted a regioselective syn carboauration of alkynes at ambient temperature (Scheme 10.143). 

N-l-Acyl and N-l-sulfamoyl derivatives are formed by the reaction of appropriate chlorides with ergolines under phase-transfer catalysis (Loncaric and Rucman, 1984, Taimr and KrSpelka, 1987). Dimethyl and diethylcarbamoyl derivatives were prepared in the same manner. N-1-Acetyl ergolines were also prepared by a reaction with acetic anhydride under catalysis with BF3 etherate (Benes, 1989). N-1 Formyl ergolines can be obtained by treatment with formic acid and a tertiary amine under palladium catalysis (Taimr et ai, 1987b). 

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