Carbonylations and acylations

2 Cobalt-, Manganese- and Iron-catalyzed Cross-coupling Reactions 9.4.2.1 Carbonylations and acylations 

The reaction of cobalt(II) salts with drganolithiums or -magnesiums leads to a fast decomposition even at low temperature, providing homocoupling products. These transmetallations have therefore found limited applications in organic synthesis [90]. It was recently reported that the reaction of organozinc compounds with cobalt(II) bromide in 

Allylic chlorides react with organozinc halides or diorganozincs in the presence of catalytic amounts of CoBr, [92]. These reactions lead to the SN2 cross-coupling product with 

A three-necked flask was charged with 5-chloro-l-iodo-l-pentene (1.8 g, 6.0 mmol) in THF (5 mL) and was cooled to — 100°C (liquid N2/ether bath), and n-BuLi (6.3 mmol, 1.6M in hexane) was added over 4 min. The resulting colorless solution was stirred at 0°C for 2min and cooled back to -78 °C. p-Toluenesulfonyl cyanide (0.90g, 5.0 mmol) in THF (5 mL) was added and the reaction mixture was warmed to room temperature and stirred for 3 h. After the usual workup and evaporation of the solvents, the crude residue obtained was purified by flash chromatography (hexane/ether, 10 1), yielding the unsaturated nitrile 10 (466 mg, 72% yield) as a clear oil (100% by GLC analysis and l3C NMR analysis). 

A 25 mL two-necked flask was charged with /3-pinene (1.36g, 10 mmol), and diethylborane (2.0 g, 10 mmol) in ether was added at 0°C. The resulting solution was stirred for 15 min, allowed to warm to 25 °C, and further stirred for 1 h. It was then cooled to 0°C, and the solvents were removed by applying high vacuum (0.1 mmHg) for 15 min at 0°C, and for 30 min at rt. The reaction mixture was cooled to 0°C and Et Zn (2mL, 20 mmol) was added. The reaction mixture was stirred for 10 min at 0°C and for 20 min at rt. It was again cooled to 0°C, and the solvents were removed as described above. The 

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Scheme 8.15. Synthesis of Ketones, Esters, Carboxylic Acids, and Amides by Palladium-Catalyzed Carbonylation and Acylation... 

Radical carbonylation can also be conducted in a zinc-induced reduction system. A similar three-component transformation reaction to that illustrated in the second equation of Scheme 6.14 can be attained using zinc and protic solvents (Scheme 6.38) [59]. The observed stereochemical outcome is identical to that for the tin hydride-mediated reaction, providing a additional evidence for free-radical generation, radical carbonylation, and acyl radical cyclization taking place simultaneously, even in the zinc-induced system. In this system, however, the final step is reduction to form a carbanion and protonation. 

CATALYSIS IN CHEMISTRY AND ENZYMOLOGY. William P. Jencks. Exceptionally clear coverage of mechanisms for catalysis, forces in aqueous solution, carbonyl- and acyl-group reactions, practical kinetics, more. 864pp. 5X x 8H. 65460-5 Pa. 18.95... 

In this chapter wc shall continue with our study of carbanion chemistry, with emphasis on the attachment of alkyl groups to the a-carbons of carbonyl and acyl compounds. Such alkylation reactions owe their great importance to the special nature of the carbonyl group, and in two ways. First, the carbonyl group makes a-hydrogens acidic, so that alkylation can take place. Next, the products... 

A further variant on the radical carbonylation/acyl radical cyclization theme involves the silylcarbonylation of 1,5-hexadienes [48]. Here, the sequence is initiated by the addition of a tris(trimethylsilyl)silyl radical to the least substituted terminus of the diene. Carbonylation and acyl radical cyclization then ensues in the normal way. It should be noted that this type of carbonylation cannot be achieved with tin hydride, since the carbonylation rate is not sufficient to capture y -tin-attached alkyl radical, which quickly reverts to tin radical and the 1,5-diene. 

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... 

We propose the unsaturated lipids of biological membranes to provide the cells with an electronic conduction band. A striking feature of the unsaturated lipids in biomembranes is the very constant location of ethylenic cw-double bond in monounsaturated acyl chains between carbon atoms 9 and 10. A noteworthy exception is nervonic add (cw-15-24 1), which is abundant in central nervous system membranes. A microviscosity barrier has been observed in bilayers of dioleoylphosphatidylchohne at the depth of the oleic acid double bonds.Phospholipids belong to lyotropic liquid crystals and possess remarkable short- and long-range order. In a cell membrane lattice the local concentration of ester carbonyls and acyl chain ethylenic double bonds as well as the local concentration of cholesterol C=C bonds is very high. 

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