Oxygen-functionalized compounds

Further complexes of Nb(V) are formed with oxygen-function compounds, such as o-dihydroxybenzene and acetylacetone. 

Oxygen-function compounds also may be subjected to ammonolysis, for example ... 

The oxo reaction is the general or generic name for a process in which an unsaturated hydrocarbon is reacted with carbon monoxide and hydrogen to form oxygen function compounds, such as aldehydes and alcohols. 

Tandem intramolecular silylformylation-allylation reaction of diallylhydrosilyl ethers derived from homoallyl alcohols is convenient for rapid, stereoselective synthesis of 1,3,5-triols convertible to more oxygen-functionalized compounds (Scheme 12).142,142a,142b 143 [ he second uncatalyzed allylation step would be facilitated by the formation of a strained silacycle intermediate, which has enough Lewis acidity to activate the formyl group. A similar tandem reaction via alkyne silylformylation has been reported.144... 

Some classes of vicinal oxygen-functionalized compounds are reduced to give stereoiso-meric products [174-180]. Cathodic reduction of benzil in acidic and neutral solutions led to the formation of cis and traw -stilbenediols. The cis—trans ratio could be determined by trapping the chemically unstable stilbenediols as the 0,0 -dimethyl derivatives during electrolysis in the presence of dimethyl sulfate [175]. The cis isomer, as expected, was always predominant. 

Another group of macrocyclic ligands that have been extensively studied are the cycHc polyethers, such as dibenzo-[18]-crown-6 (5), in which the donor atoms are ether oxygen functions separated by two or three carbon atoms. The name crown ethers has been proposed (2) for this class of compounds because of the resemblance of their molecular models to a crown. Sandwich stmctures are also known in which the metal atom is coordinated with the oxygen atoms of two crown molecules. 

These compounds generally exist in carbonyl forms. The oxygen function can be converted into halogen by phosphorus halides. Reactions with electrophiles are quite complex. Thus urazole (511) reacts with diazomethane quickly to yield (512), which is more slowly converted into (513). 1-Phenylurazole gives (514) however, 4-phenylurazole yields (515). Oxadiazolinones of type (516) can be alkylated at both O- and N-atoms. 

Acylation of various oxygen functions by use of common and commercially available fluonnated carboxylic acid denvatives such as trifluoroacetic anhydride or the corresponding acyl halides have already been discussed sufficiently in the first edition [10] Therefore only exceptional observations will be described in this section In the past 15 years, many denvatizations of various nonfluonnated oxygen compounds by fluoroacylation were made for analytical purposes. Thus Mosher s acid chlorides for example became ready-to-use reagents for the determination of the enantiomeric purity of alcohols and amines by NMR or gas-liquid chromatographic (GLC) techniques [//] (equation 1)... 

These reactions are related to the formation of pyrroles and quinolines from aminocarbonyl compounds and acetylenes (582,583) and may be contrasted with the formation of pyran derivatives by electrophilic attack on an enamine, followed by addition of an oxygen function to the imonium carbon (584-590). 

Suitable carbonyl compounds can thus be olefmated photochemicully with (diazobenzyl)diphenylphosphine oxide (7), the oxygen function being substituted by a diphenylmethylene group 18,20). Hence irradiation of 7 for a sufficient length of time in the presence of the corresponding unsaturated ketones affords the hepta-fulvene 27 23), the trans-1,3-butadiene 28 22 and the cross-conjugated hexatriene 2922> by direct olefination with the intermediate 9. 

Recently, the hydroxy derivatives of furan, thiophene, and selenophene have been studied with regard to their physical properties and reactions. These compounds are tautomeric and if the oxygen function is placed in the 2-position they exist as unsaturated lactones and undergo carbon-carbon rearrangement, whereas the 3-hydroxy derivatives form oxo-enol tautomeric systems. By NMR the structures of the different tautomeric forms have been determined as well as the position of the tautomeric equilibrium and the rate of isomerization. 

The potential synthetic utility of titanium-based olefin metathesis and related reactions is evident from the extensive documentation outlined above. Titanium carbene complexes react with organic molecules possessing a carbon—carbon or carbon—oxygen double bond to produce, as metathesis products, a variety of acyclic and cyclic unsaturated compounds. Furthermore, the four-membered titanacydes formed by the reactions of the carbene complexes with alkynes or nitriles serve as useful reagents for the preparation of functionalized compounds. Since various types of titanium carbene complexes and their equivalents are now readily available, these reactions constitute convenient tools available to synthetic chemists. 

Category I Substituent Assemblies The first rationalization of the observation that in acetal-type compounds the a-SCS of the second oxygen function is considerably smaller than that of the first (70,239) was the assumption that an adjacent oxygen atom reduces the polarizability of the a-carbon atom, so that it cannot be polarized as effectively by the second substituent (142). 

This latter compound, 36, and the isomeric 9-oxabicyclo[4.2.1]nonane, 37, were obtained as the sole products, in ca 13 87 ratio, by reaction of 3 with A-chlorosuccinimide (NCS) in protic solvents (methanol, dioxane-water mixtures)72. It is noteworthy that similar ratios of the two disubstituted bicyclononane derivatives were obtained, independently of the solvent, also by using A-bromosuccinimide (NBS) as electrophile, whereas a strongly solvent-dependent ratio was observed when A-iodosuccinimide (NIS) was used. Since these reactions should proceed through hydroxy- or alkoxyhalogenation of one of the double bonds, followed by transannular attack of the oxygen function on the cationic center which is formed on the other side of the ring by the reaction of another electrophile with the second double bond, the isomer ratio has been rationalized in terms of a different nature of the intermediates. 

Satoh T, Miura M (2007) Catalytic Arylation and Vinylation Reactions Directed by Anionic Oxygen Functions via Cleavage of C - H and C - C Bonds. 24 61-84 Savoia D (2005) Progress in the Asymmetric Synthesis of 1,2-Diamines from Azomethine Compounds. 15 1-58... 

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