Carbonyl Compounds and Organometallic Carbonyl Synthons: Syntheses, Stabilities, and New Transformations

摘要

Dihydroanisole was metalated with n-butyllithium and potassium t-butoxide in diethyl ether/HMPA at 78 C, and the resulting organometallic alkylated with methyl electrophiles. The regiochemistry of the process was elucidated and compared with other methods. Dialkylation was also explored. The hydrolysis of alkylated products afforded synthetically useful 2-substituted -2-cyclohexenones. Trimethylsilyl triflate was shown to catalytically convert the Diels-Alder adducts of Danishefsky's diene to cyclohexenones without the attendant methoxy ketone formation that had complicated earlier efforts. The keto tautomers of phenol, 2,4- and 2,5-cyclohexadienone, were generated in the gas via 4+2-cycloreversion reactions of suitable precursors. The gas phase acidites of these tautomers were measured and their heats of formation were calculated. Factors influencing the enthalpies of tautomerization to phenol were evaluated. Dimethoxy- and diethoxymethyllithium were generated via transmetalation of organotin precursors at -109C and efficiently trapped with p-anisaldehyde. The thermal stabilities of these acyclic reagents were elucidated and compared with those of cyclic dialkoxymethyllithiums. Alkylation of 2-lithio-1,3-dioxane with benzyl bromide was investigated.