An expeditious reaction sequence featuring a microwave-assisted tandem 5-exo cyclization-Claisen rearrangement process was used to assemble the A/B ring system of frondosin B. Completion of the target natural product was achieved in 38.2% yield over an eight-step linear sequence.
Utilization of the Thorpe–Ingold Effect in the Synthesis of Cyclooctanoid Ring Systems via Anionic 6-<i>exo</i>-<i>dig</i> Cyclization/Claisen Rearrangement Sequence
作者:Weston C. DeLomba、Elizabeth A. Stone、Kimberly A. Alley、Victoria Iannarone、Emily Tarsis、Sami Ovaska、Timo V. Ovaska
DOI:10.1021/acs.joc.0c01132
日期:2020.8.7
demonstrate a facile approach for the synthesis of gem-disubstituted cyclooctanoids, a motif found in several biologically active compounds. Appropriately substituted 1-alkenyl-5-pentyn-1-ols bearing gem-dialkyl substituents at either the C2, C3, or C4 position serve as useful precursors to a number of cyclooct-4-enone derivativesvia a tandem, microwave-assisted oxyanionic 6-exo-dig cyclization/Claisen
Studies on the oxidation of hydrazones with iodine and with phenylselenenyl bromide in the presence of strong organic bases; an improved procedure for the synthesis of vinyl iodides and phenyl-vinyl selenides
The oxidation of hydrazones by iodine in the presence of strong organic bases (guanidines) has been studied. Improved yields of vinyl iodides can be obtained by inverse addition using dry solvents and with a final heating period where appropriate. The reaction has been extended to various dihydrazones with interesting results.
Reactivity of acyclic (pentadienyl)iron(1+) cations: Synthetic studies directed toward the frondosins
作者:Do W. Lee、Rajesh K. Pandey、Sergey Lindeman、William A. Donaldson
DOI:10.1039/c1ob05720k
日期:——
[1-methoxycarbonyl-5-(2′,5′-dimethoxyphenyl)pentadienyl]Fe(CO)3+ cation was prepared in two steps from (methyl 6-oxo-2,4-hexadienoate)Fe(CO)3. Reaction of this cation with isopropenyl Grignard or cyclohexenyllithium reagents affords (2-alkenyl-5-aryl-1-methoxycarbonyl-3-pentene-1,5-diyl)Fe(CO)3 along with other addition products. Oxidative decomplexation of these (pentenediyl)iron complexes, utilizing CuCl2, affords
The oxidation of ketone hydrazones by iodine in the presence of a base to furnish vinyliodides has been considerably improved. The three factors responsible are (1) absence of water, (2) the use of strong guanidine bases and (3) inverse addition.