Carbonyl moiety

The rate of the Lewis-acid catalysed Diels-Alder reaction in water has been compared to that in other solvents. The results demonstrate that the expected beneficial effect of water on the Lewis-acid catalysed reaction is indeed present. However, the water-induced acceleration of the Lewis-add catalysed reaction is not as pronounced as the corresponding effect on the uncatalysed reaction. The two effects that underlie the beneficial influence of water on the uncatalysed Diels-Alder reaction, enforced hydrophobic interactions and enhanced hydrogen bonding of water to the carbonyl moiety of 1 in the activated complex, are likely to be diminished in the Lewis-acid catalysed process. Upon coordination of the Lewis-acid catalyst to the carbonyl group of the dienophile, the catalyst takes over from the hydrogen bonds an important part of the activating influence. Also the influence of enforced hydrophobic interactions is expected to be significantly reduced in the Lewis-acid catalysed Diels-Alder reaction. Obviously, the presence of the hydrophilic Lewis-acid diminished the nonpolar character of 1 in the initial state. 

Reduction. Because of a lack of discrimination between the double bond and carbonyl moieties, direct hydrogenation of acrolein leads to the production of mixtures containing propyl alcohol, C HgO [71-28-8] propionaldehyde, C H O [123-38-6J, and aHyl alcohol, C H O [107-18-16]. Both the... 

Multifunctional nucleophiles may undergo 1,4-conjugate addition to the double bond, followed by reaction at the carbonyl moiety to give heterocycHc products (15—18). 

The double-bond length in 1,3-butadiene is 0.134 nm, and the ingle-bond, 0.148 nm. Since normal carbon—carbon single bonds are 0.154 nm, this indicates the extent of double-bond character in the middle single-bond. Upon complexing with metal carbonyl moieties like Fe(CO)2, the two terminal bonds lengthen to 0.141 nm, and the middle bond shortens even more to 0.145 nm (18). 

Oxidation o( 1,2-glyools to two carbonyl moieties by teed tetraacetate (LTA). 

The mechanism of the Patemo-Biichi reaction is not well understood, and while a general pathway has been proposed and widely aceepted, it is apparent that it does not represent the full scope of reactions. Biichi originally proposed that the reaction occurred by light catalyzed stimulation of the carbonyl moiety 1 into an excited singlet state 4. Inter-system crossing then led to a triplet state diradical 5 which could be quenched by olefinic radical acceptors. Intermediate diradical 6 has been quenched or trapped by other radical acceptors and is generally felt to be on the reaction path of the large majority of Patemo-Biichi reactions. Diradical 6 then recombines to form product oxetane 3. 

In contrast to the saturated azlactones, the Friedel-Crafts reaction of 2-substituted-4-arylidene-5-oxazolones is quite complex and may follow several different courses, often concurrently, depending on both reaction conditions and structural variations in the arylidene ring. This behavior is readily interpreted in terms of the a,)S-unsaturated carbonyl moiety and the cross-conjugated system containing nitrogen, both of which provide potential reaction sites in addition to the lactone carbonyl group. The reaction has been investigated " ... 

H )-Euranones are useful building blocks in the synthesis of a variety of organic compounds. In addition, they often serve as valuable synthetic intermediates in the stereoselective construction of substituted y-butyrolactones via conjugated addition to the Q ,/3-unsaturated carbonyl moiety or catalytic hydrogenation of the double bond (88JOC1560). 

When having an Q ,/3-unsaturated carbonyl moiety, 2(5/7)-furanones are capable of undergoing 1,4-Michael-type additions. It was found that 1,4-addition reactions of thiophenols to the furanones 168,170, and 172 take place at room temperature in the presence of triethylamine to give a quantitative yield of the adducts 169, 171, and 173. Complete diastereoselective Michael-type addition occurred in all cases (Scheme 48) (88T7213). 

Introduction of an additional methyl group on the donor atom of TMM moiety gives a low 33% yield of the perhydroindans (49, X=H2) and (50, X=H2) with substantial production of the diene by-products [24]. However, it is still remarkable that the reaction works at all since the corresponding intermolecular cycloaddition failed. Incorporation of a carbonyl moiety adjacent to the donor carbon atom doubles the yield of the cycloadducts to 66% (Scheme 2.15). This so-called acyl effect works by making the donor carbon of the TMM unit "softer," thus facilitating the initial step of the conjugate addition, as well as inhibiting base-induced side reactions [22]. 

A rather distantly related analogue incorporating a 3-di-carbonyl moiety as a bioisosteric replacement for a carboxyl, aril done (55), blocks the uncoating of polio virus and herpes simplex virus type I and thus inhibits infection of cells and l.he early stages of virus replication. Thus effective therapy would require careful timing as it does with amantidine. 

The exo selecdvity of the TiCL-TADDOLate-catalyzed 1,3-thpolar cycloadthdon is improved by the tise of sticcinimide instead of oxazoiidinone as attxiliary for the a,fi-imsatitrated carbonyl moiety (Eq. 8.55). A strong bidentate coo rdinadon of the alkenyl moiety to the metal catalyst is impcrtant in these re... 

Reductive alkylation with chiral substrates may afford new chiral centers. The reaction has been of interest for the preparation of optically active amino acids where the chirality of the amine function is induced in the prochiral carbonyl moiety 34,35). The degree of induced asymmetry is influenced by substrate, solvent, and temperature 26,27,28,29,48,51,65). Asymmetry also has been obtained by reduction of prochiral imines, using a chiral catalyst 44). Prediction of the major configurational isomer arising from a reductive alkylation can be made usually by the assumption that amine formation comes via an imine, not the hydroxyamino addition compound, and that the catalyst approaches the least hindered side (57). 

Fig. 23. Space filling model of the Enniatin B—K + complex after the crystal structure 103). Since the carbonyl moieties coordinating the cation are similar for Enniatin B and Valinomycin, the difference in selectivities must arise due to the energetics of the conformations required to achieve coordination of the cation...

Thus, the dianion derived from a-amino acid substitutes the /1-chloride to give the ester of 2-(phenylsulfonyl)ethenyl amino acid and subsequent desulfonylation provides N-(benzoyl)vinylalanine methyl ester (62) (equation 61). The conjugate addition of enolates to methyl styryl sulfone (63) and subsequent intramolecular addition to the carbonyl moiety provide a synthetically valuable method for the construction of bicyclic and tricyclic skeletons52. Desulfonylation of the cyclization product 64 with sodium in ethanol-THF gives the diene 65 in good yield (equation 62). 

In one compound iron carbonyl moieties serve as electron donors to the B of a simple aminoborane, whereas the N atoms have donor functions to Fe ... 

Dibenzobicyclo[2.2.2]octadienones (34) bearing an aromatic substituent were designed to probe the unsynunetrization of the carbonyl it orbital arising from the aromatic % orbitals [103,104], Reduction of the carbonyl moiety of 2- (R H) and 3-substituted (R3 H) dibenzobicyclo[2.2.2]octadienones (34) was studied by using sodium borohydride in methanol at - 3 °C. The 2- (34a) and 3-nitrodibenzo-bicyclo[2.2.2]octadienones (34d)... 

Yeom and Frei [96] showed that irradiation at 266 nm of TS-1 loaded with CO and CH3OH gas at 173 K gave methyl formate as the main product. The photoreaction was monitored in situ by FT-IR spectroscopy and was attributed to reduction of CO at LMCT-excited framework Ti centers (see Sect. 3.2) under concurrent oxidation of methanol. Infrared product analysis based on experiments with isotopically labeled molecules revealed that carbon monoxide is incorporated into the ester as a carbonyl moiety. The authors proposed that CO is photoreduced by transient Ti + to HCO radical in the primary redox step. This finding opens up the possibility for synthetic chemistry of carbon monoxide in transition metal materials by photoactivation of framework metal centers. 

With compounds containing C—H bonds y to the carbonyl moiety, one often observes intramolecular hydrogen abstraction, in contrast to the in-termolecular hydrogen abstraction by aryl ketones discussed earlier in this... 

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