Carbon-oxygen bond forming reactions

Glycosylation of 1-glycosyl dimethyl phosphite with alcohols typical procedure 

Reductive bomo- and betero-coupling of carbonyl compounds general procedure 

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A useful assortment of carbon-carbon bond forming reactions such as alkylation of enolates and enamines and carbon-oxygen bond forming reactions such as epoxidation with ylides have been described in this chapter. 

Carbon-Carbon and Carbon-Oxygen Bond-Forming Reactions... 

Carbon - Oxygen Bond Forming Reactions at Room Temperature... 

SCHEME 1.5 Example of a rhodium-catalyzed carbon-oxygen bond-forming reaction [17]. 

This landmark discovery paved the way for the development of transition metal-catalyzed hydroboration. The conversion of an alkene into an organoborane intermediate has made this a valuable synthetic technique, particularly since the development of enantioselective variants.9,10 They serve as synthons for numerous functional groups11 and are often subjected to a consecutive carbon-oxygen, carbon-carbon, boron-carbon, boron-chlorine, or carbon-nitrogen24 bond-forming reaction (Scheme 3). 

The copper catalyzed carbon-heteroatom bond forming reactions are also efficient in the introduction of oxygen and phosphorous based substitutents onto the aromatic ring. 3-Iodopyridine was reacted with -butanol in the presence of 10 mol% copper(I) iodide and 20 mol% 1,10-phenantroline... 

The last example focuses not on the functionalization of heterocycles by a transition metal mediated carbon-heteroatom bond forming reaction, but the palladium catalyzed conversion of primary amines, including amino-heterocycles, into urea derivatives. A representative example, shown in 8.38., includes the reaction of an amino-carbazole derivative with morpholine, carbon monoxide and oxygen in the presence of catalytic amounts of palladium(II) iodide. The formation of the urea moiety proceeds with great selectivity and in high yield.49 The reaction works equally well for primary aliphatic and aromatic amines. 

Oxidative coupling of a terminal alkyne is a particularly easily performed carbon-carbon bond forming reaction, which results in a good yield of the symmetrical diacetylene. A widely used procedure involves the oxidation of the alkyne with air or oxygen in aqueous ammonium chloride in the presence of a copper(i) chloride catalyst (Glaser oxidative coupling). 

When this happens, a carbon-oxygen bond forms at the same time that the carbon-bromine bond is broken. The net result of this reaction is the substitution of an OH- ion for a Br ion. Because the reaction occurs in a single step, which involves collisions between the two reactants, the rate of this reaction is proportional to the concentration of both reactants. 

Useful intermediates and end-products obtained from biocatalysed carbon-carbon, carbon-oxygen, carbon-nitrogen and carbon-chalcogen bond-forming reactions... 

Probably the most popular carbon-carbon double-bond-forming reaction involving sulphur proceeds via the elimination of a sulphur-oxygen species. This is illustrated by a synthesis of 1,5-unsaturated dicarbonyl compounds (236) which proceeds by phenylthioalkylation of enolates (236a), using the phenyl-thioalkene (237), followed by ozonolysis and elimination of the sulphoxide moiety to provide the double bond. An alternative method for double-bond formation is shown in the preparation of alkenes R CH=CHR by reductive cleavage of the sulphide (238) with titanium salts, and demonstrates the versatility of sulphur in such double-bond formations. In the latter example... 

Need to convert an unactivated alkene into an ester Are the methods for ether/ester synthesis limited to alcohols and carboxylic acids This can be accomplished through the gold- or ruthenium-catalyzed addition of carboxylic acids to alkenes [22, 25] A number of heteroatom-containing compounds have been involved in oxygen-carbon(sp ) bond-forming reactions. The intramolecular iodinative cyclization of phosphoramidates serves as a representative example [37]... 

An interesting approach to the preparation of macrocycles has been accomplished through a series of oxygen-carbon(sp ) bond-forming reactions (Scheme 2.67) [95]. While many of the reactions described previously needed a metal catalyst to promote the formation of the ethers, this chemistry was successful without the addition of such a catalyst. Treatment of 1,4-dihydroxybenzenes with 3,6-dichlorotetrazine in acetonitrile generated the mac-rocycles in moderate to good yield. A range of functionalized 1,4-dihydroxybenzenes... 

Dotted lines are used to represent bonds that are partially broken or partially formed. The carbon-chlorine bond breaks on one side of the transition state structure while the carbon-oxygen bond forms on the other side. Transition state structures represent species that cannot be isolated because they are too short-lived and present in only infinitesimal concentrations. The structure of the transition state for a reaction is inferred from kinetic data. Transition states are not intermediates. An intermediate is a species with a finite lifetime, and some intermediates can be isolated. An intermediate forms in one reaction, has a discrete structure, and then reacts in a second reaction. 

Carbon-oxygen bonds are formed by the Ullmann reaction (- coupling of aryl halides with copper) which has been varied in alkaloid chemistry to produce diaryl ethers instead of biaryls. This is achieved by the use of CuO in basic media (T. Kametani, 1969 R.W. Dos-kotch, 1971). 

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