Cyclohexenones organometallics

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]. 

Enantioselective Conjugate Addition to Prochiral Enones of Organometallic Reagents Modified with Ephedrine. Enantioselective conjugate addition to 2-cyclohexenone with chiral organo(alkoxo)cuprates [MCu(OR )R] has been studied. When the cuprate is prepared from the lithium alkoxide of ephedrine, Phenyllithium, and Cul, 3-phenylcyclo-hexanone with 50% ee is obtained. The enantioselectivity reaches 92% ee in enantioselective ethylation when a chiral diamino alcohol derived from ephedrine is employed (eq 13). ... 

However, reaction of the same allenyl organometallic species with cyclohexenone generates only the four-membered ring cycloadduct (42) (equation 34). In Ae latter case it is likely that the (7i -alle-... 

The best control of addition of these organometallics at the C-1 site of enones is achieved by performing the reaction in a less basic solvent, such as ether or THF, at a lower temperature (-110 or -78 °C), and within a shorter time, so that not only the formation of the C-1 adducts is favored, but also there is a lower chance of them isomerizing to the more stable C-3 adducts (Scheme 152, compare f to g Scheme 153, compare a with b-d Scheme 154, compare c to a). This control is particularly efficient with cyclohexenone (Scheme 153, a and b)" and straight chain enones (Scheme 152, e)" and particularly poor with cyclopentenone (Scheme 154, a and b). Such control cannot be achieved with chal-cone (Scheme 152, a-d)." ... 

Organometallic reactions. In promoting reactions of Grignard and organolithium reagents with 2-cyclohexenone, chemoselectivity is solvent dependent. 

The procedure for oxidation of the sulfide to the sulfone is based on that reported earlier by Bordwell and Pitt. The synthetic utility of phenyl vinyl sulfone and sulfoxide derives not only from their ability to serve as excellent Michael acceptors toward such reagents as enolate anions and organometallics, but also as moderately reactive dienophiles in Diels-Alder reactions. " The resulting adducts, in turn, can be chemically modified so that these electron-deficient olefins serve as useful synthons for acetylene,ethylene,terminal olefins,vinylsilanes, and ketene in [4 + 2] cycloadditions. Phenyl vinyl sulfone undergoes ready cycloaddition to Danishefsky s diene in the first step of a protocol for the regiospecific y-alkylation of 2-cyclohexenones. Furthermore, the ready lithiation of phenyl... 

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