Reaction of Diketene with Grignard Reagents in the Presence of Cobalt Catalyst. A Convenient Method for the Synthesis of 3-Methylenealkanoic Acids Leading to Terpenoids

Abstract

Primary alkyl Grignard reagents react regioselectively with diketene in the presence of cobalt(II) iodide to afford 3-methylenealkanoic acids in good yields. The synthetic utility of this reaction is demonstrated in the syntheses of terpenoids by two methods. Utilizing the isomerization of double bond of 3-methylenealkanoic acids, geranic acid and farnesic acid were obtained in two steps. Another method, the tandem [3,3] sigmatropic rearrangement of the corresponding allylic esters was used for the synthesis of C18-Cecropia juvenile hormone.

Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions

“…Scheme ), as well as the amount of H 2 SO 4 needed to titrate the resulting precipitate, are consistent with an empirical formula [Fe(MgX) 2 ] n . Apparently, the reduction of FeX n effected by the Grignard reagent does not stop once a zerovalent iron species is generated, but ultimately leads to compounds in which the iron center is distinguished by a formally negative oxidation state and a d electron configuration.…”

“…Cross coupling in general, however, is by no means confined to the use of group 10 metals. In fact, one may see the immediate roots of the field in early contributions to organonickel chemistry, which themselves were predated by notable reports on the use of iron salts for the cross coupling of Grignard reagents with various organic electrophiles. – These results found surprisingly little echo for a long period of time, in part because they were overshadowed by the triumph of their nickel- and palladium-based relatives discovered shortly thereafter. It is only recently that iron-catalyzed processes regain considerable attention, paralleled by an equally growing interest in the use of cobalt for similar purposes .…”

Sesquiterpenoids synthesis

“…The derived aldehyde (2) has been converted into p-farnesene (3), p-sinensal (4), and dendrolasin (5) (Scheme 1). Another synthesis of dendrolasin ( 5 ) has been achieved4 by the alkylation of the trimethylsilyl ester anion derived from (6) with bromoacetaldehyde, which proceeds in high yield to give the P-hydroxylactone (7). Dehydration of (7) followed by reduction with BulAlH and acidic work-up gave dendrolasin (5) (Scheme 2).…”

Efficient and Stereo-Selective Syntheses of Three Stereoisomers of the Sex Pheromone of the Cowpea Weevil,Callosobruchus maculatus

“…In connection to our studies on the copulation release pheromone of C. maculatus, we were interested in the stereoselective synthesis of the sex pheromones of C. maculatus. Isomerization of 4 to 2 and 3 has been reported by Fujisawa,9) so we decided to develop an efficient and stereoselective procedure for the syntheses of 4, 5 and 6.…”