Cyclohexenones from

FUJIMOTO - BELLEAU Cyclohexenone Synthesis Synthesis of fused cyclohexenones from lactones (an alternative to the Robinson annulation). 

Knochel et al. described Pd-catalyzed Negishi cross-coupling reactions between zinc organometallics and aryl iodides in [BMMlM][Bp4]. Scheme 5.2-20 illustrates the reaction for the formation of a 3-substituted cyclohexenone from 3-iodo-2-cyclo-hexen-l-one [82]. 

N. Chida, M. Ohtsuka, K. Ogura, and S. Ogawa, Synthesis of optically active cyclohexenones from carbohydrates by catalytic Ferrier rearrangement, Bull. Chem Soc. Jpn. 64 2118 (1991). 

A much more generally useful process was developed by Robinson to prepare cyclohexenones from ketones and methyl vinyl ketone or its derivatives. Again, because good compilations of the Robinson annulation exist,8 only a few examples are given here. The first step of this process, the Michael addition, is carried out by normal base catalysis, while the second step, the aldol condensation, is best accomplished by the use of a secondary amine to form the enamine of the acyclic ketone, which then cyclizes... 

Diastereoselective reduction of chiral fl-keto sulfoxides1 (13, 115-116). This reaction, which can be controlled to provide either diastereomer of a chiral P hydroxy sulfoxide, has been used to obtain (R)- or (S)-4-hydroxy-2-cyclohexenones from the monoketal (2) of 1,4-cyclohexanedione. Sulfinylation of 2 with (S)-( —)-... 

N. Chida, M. Ohtsuka, K. Ogura, and S. Ogawa, Synthesis of optically active cyclohexenones from carbohydrates by catalytic Ferrier rearrangement, Bull. Chem. Soc. Jpn. 64 2118 (1991). A. S. Machado, A. Olesker, and G. Lukacs, Syntheses of two enantiomeric tetrasubstituted cyclohenanones from 6-deoxyhex-5-enopyranoside derivatives, Carbohydr. Res. 735 231 (1985). 

A route to 2-cyclohexenones from manganese c to effect the cyclization. ... 

Birch reduction of aromatic ethers is well known to afford alicyclic compounds such as cyclohexadienes and cyclohexenones, from which a number of natural products have been synthesized. Oxidation of phenols also affords alicyclic cyclohexadienones and masked quinones in addition to C—C and/or C—O coupled products. All of them are regarded as promising synthetic intermediates for a variety of bioactive compounds including natural products. However, in contrast to Birch reduction, systematic reviews on phenolic oxidation have not hitherto appeared from the viewpoint of synthetic organic chemistry, particularly natural products synthesis. In the case of phenolic oxidation, difficulties involving radical polymerization should be overcome. This chapter demonstrates that phenolic oxidation is satisfactorily used as a key step for the synthesis of bioactive compounds and their building blocks. 

We were able to detect and segregate the polychlorinated cyclohexenones from the chlorination reaction masses. 

I, 5-dicarbonyl compounds and their interesting and varied chemistry, e.g., the formation of cyclohexenones from aldol condensation of the products. As an extension of the de Mayo reaction (the photocycloaddition of enolated /i-diketones to double bonds) enol esters, enol ethers, vinylogous esters and amides, and dioxinone have been employed as the enone components. Some intermolecular examples have already been discussed in Section 1.6.1.4.2.1.6. (cf. Table 4, entries 2 and 3) and some intramolecular systems are collected in Table 5, entries 10,... 

Dioxo compounds cyclohexenones from, 71—73 reductive cyclization of, 41 synthesis of, 71-73... 

Also Pdotalyzed Negishi cross-coupling reactions have been described in ionic liquids. Knochel and coworkers investigated the reaction between organometalhc zinc compounds and aryl iodide in [BMMIM][Bp4] using an ionic phosphine ligand. Scheme 5.3-30 illustrates the reaction for the formation of a 3-substituted cyclohexenone from 3-iodo-cyclohex-2-en-l-one [170]. The reaction vras carried out in an ionic liquid/toluene biphasic system, which allowed easy product recovery from the catalyst by decantation. However, attempts to recycle the ionic catalyst phase resulted in significant catalyst deactivation, after only the third recycle. 

An early example of an asymmetric domino Michael/Knoevenagel reaction was reported by Jorgensen et al. [167] in 2006, providing the synthesis of chiral cyclohexenones from the reaction of tert-butyl 3-oxobutyrate and a, 3-unsaturated aldehydes catalyzed by chiral diphenylprolinol silyl ether derivative. Soon after, the... 

Scheme 12.37 Synthesis of an enantiomeric cyclohexenone from d-ghirose.

In 2010, Carter and co-workers [47] and Kotsuki and co-workers [48] reported independently the highly enantioselective synthesis of cyclohexenones from a,a-disubstituted aldehydes and enones. In both cases, the results were excellent. In Kotsuki s paper the catalyst was a primary ammonium carboxylate, concretely... 

Synthesis of 6-subst. 3-acoxy-2-cyclohexenones from 1,3-cyclohexanediones... 

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