Carbon-metal bonds, copper® acetate

M[pz(A4)] A = S2ML2. The octakis(.V-R)porphyra/,ines reported by Schramm and Hoffman (2), M[pz(S-R)8 (M = Ni, Cu), (60), can be converted to the octathiolate M[pz(S )g] (Scheme 11) via reductive cleavage of the sulfur-carbon bond when R = benzyl (Bn), and this tetra-bis(dithiolate) can then be peripherally capped with metal-ligand systems to yield peripherally tetrametalated star porphyrazines. The benzyl dinitrile 57 can be macrocyclized around magnesium butoxide to form [Mg[pz(S-Bn)8] (58) (35-40%), which can then be demetalated with trifluoroacetic acid to form 59 (90%), which is subsequently remetalated with nickel or copper acetate to form 60a (95%) and 60b (70%) (Scheme 11) (3, 23, 24). Deprotection of 60a or 60b with sodium in ammonia yields the Ni or Cu tetra-enedithiolates, 61a or 61b to which addition of di-ferf-butyl or n-butyl tin dinitrate produces the peripherally metalated star porphyrazines 62a (37%), 62b (80%), and 62c (41%). 

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. 

Ruthenium- and rhodium-catalytic systems for the direct cross-dehydrogenative coupling (CDC) of acrylamides with electron-deficient alkenes forming (Z, )-dienamides using copper(II) acetate as the oxidant has been developed. Both methods exhibit wide functional group compatibility and substrate flexibility. It is proposed that the reaction is initiated by cyclometalation of acrylamide by amide-directing C-H bond activation. Coordination of the alkene to the metal centre, followed by insertion of the carbon-carbon double bond, forms a seven-membered ruthacycle or rhodacycle species. Subsequent -elimination occurs to afford the desired (Z, )-dienamide. A CDC between two heteroarenes is effected with copper(II) acetate in the absence... 

The cyclopropanation of alkenes, alkynes, and aromatic compounds by carbenoids generated in the metal-catalyzed decomposition of diazo ketones has found widespread use as a method for carbon-carbon bond construction for many years, and intramolecular applications of these reactions have provided a useful cyclization strategy. Historically, copper metal, cuprous chloride, cupric sulfate, and other copper salts were used most commonly as catalysts for such reactions however, the superior catalytic activity of rhodium(ll) acetate dimer has recently become well-established.3 This commercially available rhodium salt exhibits high catalytic activity for the decomposition of diazo ketones even at very low catalyst substrate ratios (< 1%) and is less capricious than the old copper catalysts. We recommend the use of rhodium(ll) acetate dimer in preference to copper catalysts in all diazo ketone decomposition reactions. The present synthesis describes a typical cyclization procedure. 

The less highly substituted bond of a siloxycyclopropane is quantitatively opened by mercury(II) acetate to afford -mercurio ketones. In the same pot these are transformed to a-methylene ketones in virtually quantitative yield on treatment with one equivalent of palladium(II) chloride in the presence of lithium chloride and lithium carbonate (2 equiv each). Catalytic amounts of palladium(II) chloride (0.1 equiv) are sufficient in the second step, if two equivalents of copper(II) chloride is added as an oxidant. Mechanistically, the second step involves trans-metalation to a j -palladio ketone followed by /i-hydride elimination. In bicyclic systems it is sometimes necessary to add triethylamine to avoid HPdCl induced double-bond shifts in the reaction product. Examples are the rearrangements of 18, 20 and 22. ... 

Organocuprates and a few other carbon nucleophiles sometimes react with allylic halides (or acetates) to give the product of what looks like an SN2 reaction. However, the mechanism is completely different— preliminary coordination by the copper or other transition metal to the C=C n bond is the first step, and the coordination of the copper changes from rj-2 to rj-1 or rj-3 before a reductive elimination step establishes the C—C bond.394 Each of these steps affects the overall regiochemistry (and the stereochemistry discussed in the next chapter), which may look like an SN2 or an SN2 reaction, while mechanistically being neither. 

Propiolic Acid, HC=C.COOH, is a liquid with a pungent odor resembling that of acetic acid. After freezing it melts at 9°. It can be distilled without decomposition only under diminished pressure. It is interesting on account of the fact that its reactions show clearly its relation to acetylene. It forms as an acid, well characterized salts, and as a triple bonded compound, metallic derivatives, which result from the replacement of the hydrogen atom joined to carbon by silver or copper. When the acid is treated with an ammoniacal solution of silver nitrate a colorless, crystalline salt is formed, which soon turns yellow and explodes when struck. Propiolic acid may be prepared by the action of carbon dioxide on the sodium derivative of acetylene —... 

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