Ketones P-alkoxy

One of the first examples of 8-hydrogen abstraction in acyclic ketones was the photocyclization of P-alkoxy ketones, in particular of P-ethoxypropiophenone (34), to the corresponding furanol derivatives 37 (Scheme 8.10). It was revealed that formation of enol 36 as well as a reversion to the starting ketone occur by 1,4-hydrogen transfer from the 1,5-biradical 35 causing the lower quantum efficiency for cyclization [12]. 

Wagner, P.J. and Zepp, R.G. (1971) y- vs 8-hydrogen abstraction in the photochemistry of p-alkoxy ketones. Overlooked reaction of hydroxy... 

Aldol-type reactions. Trityl perchlorate catalyzes an aldol-type reaction between silyl enol ethers and acetals or ketals to give p-alkoxy ketones. The yields are comparable to those obtained with TiCU (6, 594). The iyn-aldol is formed predominantly ( 4 1). 

The oxidation of various allyl ethers and acetates with internal alkenes using PdCl2/CuG/02 or PdCl2/p-benzoquinone catalyst systems gave the corresponding p-alkoxy ketones regioselectively (equation 19). No a-alkoxy or o-acetoxy ketone was detected. 

In the oxidation of 2-octenyl acetate, in addition to the normal oxidation, palladium-catalyzed allylic rearrangement and subsequent oxidation took place to give a small amount of 3-acetoxy-2-octanone as a byproduct. Ethers of secondary allylic alcohols also underwent the regioselective oxidation to give the corresponding p-alkoxy ketones in 30-40% yields. But in this case too, by-products derived from the allylic rearrangement and subsequent oxidation were also detected. Results of the oxidation of some allyl ethers are shown in Table 3. ... 

Alcohols add to conjugated ketones with a PMe3 catalyst to give the p-alkoxy ketone.The conjugate addition of peroxide anions (HOO and ROO ) to cx,p-unsaturated carbonyl compounds is discussed in 15-48. 

High diastereoselectivities in p-chelation-controlled reactions have also been observed with aldehydes and ketones in the presence of a Lewis acid where the chiral center is 3 to the carbonyl group, resulting in 1,3-asymmetric induction - The high diastereoselectivity observed in the reaction shown below, using Lil as the Lewis acid arises from 3-chelation of both the ketone and the ether oxygen with Li. This locks the conformation of the P-alkoxy ketone chain, and the hydride attacks from the less hindered side. ... 

The substrate structure was extended from P-ketoesters not only to similar analogues, such as 1,3-diketones [59], P-alkoxy ketones [60] and a-ketosulfones [61], but also to simple alkanones such as 2-octanone [62],... 

Ethyl tetrahydrofuran-2-carboxylates. p-Alkoxy carbonyl compounds in which the alkoxy group is readily detached in the presence of a Lewis acid undergo condensation with ethyl diazoacetate. Tin(IV) chloride is a suitable catalyst for P-alkoxy aldehydes, but it requires zirconium(IV) chloride to effect a reaction with P-alkoxy ketones. 

BFj OEtj) are not effective at all. The reactiot excellent yields of P-alkoxy ketones. ... 

P-Alkoxy ketones and y-acetoxy ketones prepared by the oxidation of allyl ethers and homoallyl acetates, respectively, are synthetically useful intermediates. The reaction of (93) in the presence of excess sodium methoxide with 2-methylcyclohexanone afforded methyloctalone (94) in 42% yield (equation... 

D. Schultz, N. R. Schultz, J. Babij, D. Wolfe, Adv. Synth. Catal. 2012, 354, 3451-3455. Intermolecular gold(I)-catalyzed alkyne carboalkoxylation reactions for the multi-component assembly of P-alkoxy ketones. 

In 2005, the group of Nicolaou reported the total synthesis of the biomimetic (-l-)-rugulosin (15) by employing an impressive one-pot, seven-step cascade sequence (Scheme 13.2) [3]. Following the biosynthetic proposals of Shibata and the preliminary experimental results of Nicolaou, a major obstacle to the synthesis of the natural product was the presence of p-alkoxy ketone moieties in both the monomeric ketone 7 and the dimeric intermediates, as these alkoxy groups were very prone to elimination and subsequent aromatization of the resulting cyclohexenone ring. Nicolaou... 

Lil as an Additive for Organometallic-Mediated Transformations. The syn/anti selectivity in the reduction of p-alkoxy ketones is markedly increased by the addition of Lil (eq 6). ... 

Silyl enol ethers react with acetals at —78 °C to form p-alkoxy ketones. In intramolecular reactions, six-, seven-, and eight-membered rings are formed. With 1,3-dioxolanes (acetals), 1-2 equiv of TiCU leads to pyranone formation (eq 16), whereas no cyclization products are obtained with SnCU or ZnCU. ... 

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