Carbonyls ketone

Once the butadiene/metal-carbonyl/ketone (or aldehyde or nitrile) template coupling at the Group 4 bent metallocene unit has been carried out and subsequent modifications have been made, the corresponding 

It seems unlikely then that carbonyl (ketone and aldehyde) formed by thermal breakdown of hydroperoxides are important sensitisers for photo-oxidation of LDPE in normally processed polymers. The evidence is consistent with the theory that allylic hydrx>perx>xlde derived from vlnylidene is the importeuit photo-initiator initially present under these conditions. Vlnylidene disappears as a concomitant of hydroperx>xide photolysis, initiating photo-oxidation in a manner analogous to its function in thermal oxidation. 

Due to the properties of the cx-hydrogen and carbonyl ketones and aldehydes exist at room temperature as enol tautomers. Tautomerization involves a proton shift, in this case from the a-carbon position to the carbonyl oxygen position. Both tautomers exist at room temperature, but the ketone or aldehyde tautomer is usually favored. Tautomerization is a reaction at equilibrium, not a resonance. (Remember, in resonance structures atoms don move and neither resonance structure actually exists.) 

The absolute configurations of the product alcohols of acyclic ketone reductions can be reliably predicted for many oxidoreductases by using the Prelog rule (Scheme 6). More complex models are required for cyclic ketones, as will be seen later. For a given substrate, oxidoreductases are usually available that deliver hydride equivalents from opposite enantiotopic faces. This can be exploited to produce either alcohol enantiomer at will, as noted in Scheme 7 by the reduction of (13) to either (R)- or (S)-(14). Organometallic ketones can also be reduced with enantiotopic specificity. This is demonstrated by the conversions (Scheme 8) of the ferrocenyl and chromium carbonyl ketones (15) (16) and (17) 

HO and HOO can be eliminated from LOOK, respectively yielding an internal carbonyl (ketone) (Reaction 79a) and a desaturated product with an additional double bond (Reaction 79b) (391, 392). These are not major reactions, but nevertheless account for some of the hpid oxidation products identified under various conditions. 

One common chromophore frequently encountered in a number of polymers is the carbonyl ketone which shows a weak n-n transition band centered at 280 nm but extending into the UV-B region. Polymers containing this chromophore undergo two types of photochemical reaction (Scheme 15.2)  

Base Catalyzed. Depending on the nature of the hydrocarbon groups attached to the carbonyl, ketones can either undeigo self-condensation, or condense with other activated reagents, in the presence of base. Name reactions which describe these conditions include the aldol reaction, the Darzens-Claisen condensation, the Claisen-Schmidt condensation, and the Michael reaction. 

SYNS CYCLOPROPANE, l-(N-AMINO)CARBAMOYL-2-METHYL- HYDRAZINE, N-((2-METHYLCYCLOPROP-YL)CARBONYL)- KETONE, 2-METHYLCYCLOPROP-YL HYDRAZINO USAF A-14980 

Compounds include alcohols, acids, esters, carbonyls, ketones, and other hydrocarbons. However, a particular ketone l-(4-hydroxy phenyl)-3-butanone has an odor very much like raspberry [7,30]. This particiilar ketone, i.e., raspberry ketone, is sold under trade names Frambinon (Dragoco) and Oxyphe-nylon (IFF). In Hawai, the acetate of raspberry ketone is used under the trade name of Cue-Lure CAS No. [3572-06-3] to attract the harmhil melon-fly, Dacus Curcurbitae. 

There are a series of communications about the formation of dihydroazines by direct reaction of urea-like compounds with synthetic precursors of unsaturated carbonyls—ketones, containing an activated methyl or methylene group. The reaction products formed in this case are usually identical to the heterocycles obtained in reactions of the same binuclephiles with a,(3-unsatu-rated ketones. For example, interaction of 2 equiv of acetophenone 103 with urea under acidic catalysis yielded 6-methyl-4,6-diphenyl-2-oxi- 1,6-dihydro-pyrimidine 106 and two products of the self-condensation of acetophenone— dipnone 104 and 1,3,5-triphenylbenzene 105 [100] (Scheme 3.32). When urea was absent from the reaction mixture or substituted with 1,3-dimethylurea, the only isolated product was dipnon 104. In addition, ketone 104 and urea in a multicomponent reaction form the same pyrimidine derivative 106. All these facts suggest mechanism for the heterocyclization shown in Scheme 3.32. 

Other applications of this method include, e.g. the synthesis of the antibiotic A26771B (5i) [118] and the marine cembranolide isolobophytolide [119], Trost and Warner [120] reported that a-sulfonyl sulfones can also serve as the substrates of ir-allylpalladium complexes for macrocyclization. Furthermore, an a-hydroxy-carbonyl ketone was alkylated intramolecularly by a a-allylpalladium complex in the total synthesis of the macrocyclic sesquiterpene humulene [121]. 

As in the cases of termination by lactonization and lactamization, some specially structured alkenes, such as norbomene and related alkenes, can participate in intermolecular carbopalladation-carbonylative ketonization tandem processes. In the reactions shown in Scheme 22, the acylpalladium intermediates undergo intramolecular acylpalladation with arenes to provide ketones.  

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