Ketones aryl alkenyl

Alkenyl aryl ketones. The addition of salicyl aldehydes across a triple bond produces enones. 

In the total synthesis of strychnine, Overman prepared the alkenyl aryl ketone 67 in 80 % yield by the carbonylation of the aryl iodide 65 with the alkenylstannane 66 using AsPhs as a ligand [31]. 

A phosphine-Schiff base ligand (17) has been used for copper-catalysed asymmetric conjugate addition of diethylzinc to various ( )-alkenyl aryl ketones where the aryl ring is either a phenyl group substituted by nitro, chloro, or methoxy groups or not substituted or a naphthyl group. When the conjugate addition has been performed in ethyl acetate... 

Despite the great success of the transmetalation process in the enantiose-lective arylation of ketones, its extension to allylation or alkynylation reactions failed, providing the corresponding tertiary alcohols with enantiomeric excesses never higher than 50% ee. On the other hand, more success has been found in the alkenylation of ketones. The process started with the hydrozirconation of terminal alkynes to give the corresponding alkenylzirconium intermediates, which were transmetalated by reaction, in this case, with various ketones in the presence of the HOCSAC ligand. This protocol tolerated the presence of other carbon-carbon multiple bonds on the alkyne, as well as different functionalities and achieved excellent results for alkyl ketones, a,(3-unsaturated ketones and even dialkylketones, as shown in Scheme 4.22. 

As Table 5 indicates, alkyl aryl ketones are the best substrates for this reaction. This has also been the case for the previously developed chiral ligand systems. Nevertheless, there have been substantial improvements in enantioselectivity for the reactions of alkenyl methyl ketones and alkyl methyl ketones, using Rh-catalysts with chiral ligands 195a191, 206b207, and 207209. 

E. Katayama, T. Yokozawa, T. Ikaeiya, and R. Noyori, Asymmetric hydrogenation of alkenyl, cyclopropyl, and aryl ketones. RuCl2(xylbinap)(l,2-diamine) as a precatalyst exhibiting a wide scope, J. Am. Chem. Soc. 1998, 120, 13529-13530. 

The use of C-H bonds is obviously one of the simplest and most straightforward methods in organic synthesis. From the synthetic point of view, the alkylation, alkenylation, arylation, and silylation of C-H bonds are regarded as practical tools since these reactions exhibit high selectivity, high efficiency, and are widely applicable, all of which are essential for practical organic synthesis. The hydroacylation of olefins provides unsymmetrical ketones, which are highly versatile synthetic intermediates. Transition-metal-catalyzed aldol and Michael addition reactions of active methylene compounds are now widely used for enantioselective and di-astereoselective C-C bond formation reactions under neutral conditions. 

Most tosylhydrazone sodium salts could be usually Isolated from the reaction of the corresponding tosylhydrazones with sodium methoxide. However, a number of more functionalized hydrazone sodium salts, such as those derived from alkenyl aryl (25) sulfonyUiydrazones, ketone sulfonylhydrazones, and trimethylsi-lylacrolein sulfonylhydrazones, could not be isolated and an in situ salt generation procedure using NaHMDS was developed. A mixture of the desired hydrazones and NaHMDS was stirred at —78 °C then concentrated down before the addition of rhodium... 

Scheme 4.14 Ir-catalyzed transformation of aryl ketones to alkenylated products as described by Tsuchikama et al. [89].

Palladium(0)-catalyzed asymmetric arylation of tert-cyclobutanol 33 with bromobenzene, involving enantioselective C-C bond cleavage, furnished the chiral y-arylated ketone 34 (Scheme 3.13) [24]. Good enantioselectivity was observed when a chiral ferrocenyl P,N-ligand was used. y-Alkenylated and y-allenylated ketones were also obtained by asymmetric ring opening. 

Abe, S. Miyaura, N. Suzuki, A. 1992. The palladium-catalyzed cross-coupling reaction of enol acetates of a-bromo ketones with 1-alkenyl-, aryl-, or alkylboron compounds A facile synthesis of ketones and their enol acetates. J. Am. Chem. Soc. 65 2863-2865. 

The one-pot Barbier-type addition of alkenyl, aryl, allyl, vinyl, propargyl, alkynyl, or allenylchromium compounds to aldehydes or ketones is known as the Nozaki-Hiyama-Kishi (NHK) reaction. An excellent review by Furstner published in 1999 detailed the exhaustive literature on the carbon-carbon bond formations involving organochromium(III) reagents. This chapter will present major developments and examples of recent carbon-carbon bond formation methodology and improvements as well as their use in natural products synthesis since 1999. 

Contrary to organolithium or organomagnesium compounds, organomanganese halides add chemoselectively to aldehydes in the presence of ketones (Scheme 13.6) [12]. The scope of the reaction is very large since n- or s-alkyl, alkenyl, aryl and alkynylmanganese halides are always completely aldehyde-selective at room temperature, in ether as in THF. 

Aryl or alkenyl halides attack the central carbon of the allene system in the 2,3-butadien-l-ol 120 to form the 7r-allyl intermediate 121, which undergoes elimination reaction to afford the o,/3-unsaturated ketone 122 or aldehyde. The reaction proceeds smoothly in DMSO using dppe as a ligandflOl]. 

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