Ketones, addition onto

On the other hand, since oxime ethers were electrochemically more inert than ketones under the electroreduction conditions, the electroreductive intra- and inter-molecular coupling of ketones with oxime ethers proceeded via anion radicals in good yields (equations 5 and 6) °4i. Moreover, cobaloxime-mediated intramolecular radical addition onto oxime functions in the electrolysis media proceeded to afford the cyclized aminoethers (equation 7). ... 

Lithiation of aliphatic 1-acylbenzotriazoles 833 followed by 1,4-addition onto ogfl-unsaturated ketones affords anti-3-alkyM,6-diaryl-3,4-dihydropyran-2-ones 834 via ring closure of the enolate intermediate 835 (Scheme 235, Table 34) <2002JOC3104>. 

Photohydroalkylations are in most cases carbon-centered radical conjugate additions onto electron-deficient olefins [7]. Scheme 3.3 summarizes in detail the pathways for the photogeneration of radicals from R-H(Y) 1. In path a, a photocatalyst P (when excited) cleaves homolytically a suitable C—H bond, and the resultant radical adds to the olefin 2 to form the adduct radical 3. a,(3-Unsaturated nitriles, ketones, and esters... 

Indolines can also be prepared by radical cyclization. For example, the precursor 62 was annulated to the indoline 63 with incorporation of a N-substituent originating from the ketone component (Equation 16). This reaction seems to proceed via aryl radical addition onto an initially formed imine <20010L1009>. 

A-Acyl imines of fluoroalkyl ketones react exothermically with kctcncs and under mild conditions with enol ethers and alkenes to fonn [4+2] cycloadducts (Table 9). They also react with dipoles. In contrast to reactions with sulfonyi imines, competitive [2 + 2] or [2 + 1] cycloadditions or additions onto the imine function are not observed. The strong heterodiene properties of A-acyl imines are illustrated by the reactions of methyl 3.3.3-trifluoro-2-(tri-fluoroacetyliniino)propanoate with dienes which al.so provide 1,3-oxazines as the major product. The minor product is the result of [4 + 2] cycloaddition of the diene with the imine function (Table 9. final entry). ... 

Exploration of the reduction of dicarbonyl compounds has centered on attempts to achieve intramolecular coupling of radical intermediates to give a cyclic 1,2-diol. A mechanistic study of the production of cyclopropanediols, during the reduction of 1,3-dibenzoylpropane in acetonitrile, has been made [110]. It is suggested that the ratedetermining cyclization step is the addition of the radical anion from one ketone function onto the second carbonyl group in the same molecule. 

The nucleophilic Michael-type addition onto a,j9-unsaturated ketones is one of the most powerful reactions for carbon-carbon bond formation. This reaction which is promoted under pressure [169] is accelerated in water due to the hydro-phobic effect as already postulated (see Sect. 3). In fact, various 1,3-diketones, such as l,3-cyclopentadione,have been shown to add readily to a,j9-unsaturated ketones in good yields without any catalyst (Scheme 32) [170]. 

Unbranched and substituted alkyl carbamates, such as 146 or 147 [62,88] do not cause any problems in the deprotonation step. Deuteration (with CH3OD or dissolved CH3CO2D), methoxycarbonylation (gaseous CO2, followed by diazomethane after work-up or methyl chloroformate), alkylation with methyl iodide, substitution with trialkylsilyl chlorides, trialkyltin chlorides and even tri-methyllead bromide, addition onto aldehydes and ketones, and acylation with acid chlorides or esters, all proceed without difficulties. Although a ketone is formed in the latter reactions, which is at least 15 orders of magnitude thermodynamically more acidic than the alkyl carbamate we never observed enolate formation, racemization or epimerization - with one exception it occurred to some extent after formylation with formate esters [79]. 

Addition onto aldehydes or ketones to form cyanohydrin derivatives... 

The behavior of 2-furyl vinyl ketone is similar to that of 2-vinylfuran, in which the monomer is activated in the normal fashion by the primary radical (addition onto the vinylic bond), but the formed polymer chains act as radical traps through their pendant furan ring. Thus at a critical polymer concentration practically all primary radicals are quenched to form stable furyl radicals, and normal initiation cannot take place. This phenomenon of self-retarding is also responsible for the low molecular weight [353]. 

At the start of this work, the dual nucleophilic-electrophilic character of the a-sulfonyl carbanion 213 created some problems since this anion could react not only with the carbonyl derivative (aldehyde or ketone) but also with itself, generating via this competitive pathway some homocoupling by-products. However, a wise selection of the sulfone electrophilic substituent and the use of Barbier-type conditions considerably increased the chemoselectivity of the addition reaction and directed the addition onto the carbonyl function. Benzothiazole derivatives (hereafter denoted BT) were the first substrates to be utilized in this process. After some fine tuning, they proved to be suitable candidates, affording the desired alkenes with a reasonable efficiency (Table 3.11). 

A mixture of senecioyl chloride (0.1 mol) and A1C13 (0.1 mol) in dichloromethane (50 ml) was added dropwise over 45 min with stirring to a solution of dimethylallyltrimethylsilane (O.llmol) in dichloromethane (KK)ml), previously cooled to — 60 °C. The reaction mixture was maintained at this temperature for 10 min after the final addition, and then poured slowly onto a mixture of crushed ice and ammonium chloride. After washing of the organic layer with brine and drying, artemisia ketone (0.09 mol, 90%). b.p. 87°C/200mmHg, was obtained. 

The hydration of triple bonds is generally carried out with mercuric ion salts (often the sulfate or acetate) as catalysts. Mercuric oxide in the presence of an acid is also a common reagent. Since the addition follows Markovnikov s rule, only acetylene gives an aldehyde. All other triple-bond compounds give ketones (for a method of reversing the orientation for terminal alkynes, see 15-16). With allqmes of the form RC=CH methyl ketones are formed almost exclusively, but with RC=CR both possible products are usually obtained. The reaction can be conveniently carried out with a catalyst prepared by impregnating mercuric oxide onto Nafion-H (a superacidic perfluorinated resinsulfonic acid). ... 

Properly substituted phosphonates, which serve as key intermediates for the synthesis of biologically active compounds [39,54], have been prepared via the photo-induced 1,4-addition of phosphites onto Michael ketones (Scheme 19). 

Scheme 19 1,4-Addition of phosphite onto Michael ketones via photoinduced SET...

Lavallee, J.-F. Berthiaume, G. Deslongchamps, P. Grein, F. Intramolecular Michael addition of cyclic P-keto esters onto conjugated acetylenic ketones. Tetrahedron Lett. 1986, 27, 5455-5458. 

Tsunogai and Nozaki [6] analysed Pacific Oceans surface water by consecutive coprecipitations of polonium with calcium carbonate and bismuth oxychloride after addition of lead and bismuth carriers to acidified seawater samples. After concentration, polonium was spontaneously deposited onto silver planchets. Quantitative recoveries of polonium were assumed at the extraction steps and plating step. Shannon et al. [7], who analysed surface water from the Atlantic Ocean near the tip of South Africa, extracted polonium from acidified samples as the ammonium pyrrolidine dithiocarbamate complex into methyl isobutyl ketone. They also autoplated polonium onto silver counting disks. An average efficiency of 92% was assigned to their procedure after calibration with 210Po-210Pb tracer experiments. 

---