Synthesis of Tertiary Cyclobutanols through Stereoselective Ring Expansion of Oxaspiropentanes Induced by Grignard Reagents
作者:Angela M Bernard、Costantino Floris、Angelo Frongia、Pier P Piras
DOI:10.1016/s0040-4020(00)00369-0
日期:2000.6
The stereoselectivity of the ringexpansion of oxaspiropentanes to cyclobutanols induced by Grignard reagents has been studied. It has been found that the reaction occurs through the intermediacy of a cyclobutanone, formed stereospecifically, whereas the attack of the Grignard reagent on the carbonyl group of the cyclobutanone is stereospecific only in the case of the oxaspiropentanes derived from
2,2-Dimethyl cyclopentanones by acid catalyzed ring expansion of isopropenylcyclobutanols. A short synthesis of (±)-α-cuparenone and (±)-herbertene
作者:Angela M. Bernard、Angelo Frongia、Francesco Secci、Pier P. Piras
DOI:10.1039/b505707h
日期:——
catalyzed ring expansion of isopropenylcyclobutanols; the method allows ready access to the family of sesquiterpenes cuparanes and herbertanes, as demonstrated by the synthesis of (+/-)-alpha-cuparenone and the direct precursor of (+/-)-herbertene.
A photocatalyzed oxidation of functionalized cyclobutanones to access γ-lactones has been performed in acetonitrile at room temperature, using 9,10-anthraquinone as catalysts in the presence of TFA. The process furnish good to excellent yields of the desired compounds in 4–16 h reaction and after simple filtration of the recyclable catalyst.
Stereospecific palladium(0)-catalyzed reduction of 2-cyclobutylidenepropyl esters. A versatile preparation of diastereomeric monoterpenoids: (±)-fragranol and (±)-grandisol
作者:Angela M Bernard、Angelo Frongia、Francesco Secci、Giovanna Delogu、Jean Ollivier、Pier P Piras、Jacques Salaün
DOI:10.1016/j.tet.2003.09.074
日期:2003.11
Mixtures of (E and Z)-2-cyclobutylidenepropyl sulfonates, readily available from alpha,alpha-disubstituted cyclobutanones arising from suitable cyclopropane derivatives ring expansion, underwent regioselective and stereospecific reduction by formate anion to offer, through pi-1, 1-trimethyleneallylpalladium complexes formed upon treatment with palladium(O), a new and convenient entry to the diastereomeric four-membered ring monoterpenoids (+/-)-fragranol and (+/-)-grandisol. (C) 2003 Elsevier Ltd. All rights reserved.
Synthesis of New Heterocycles through a Cation-Driven Tandem Ring-Enlargement−Annulation Reaction
作者:Angela M. Bernard、Enzo Cadoni、Angelo Frongia、Pier P. Piras、Francesco Secci
DOI:10.1021/ol026199x
日期:2002.7.1
[GRAPHICS]The thionium ion, generated through a cyclopropylcarbinyl-cyclobutyl ring expansion, is, for the first time, intramolecularly intercepted by activated aromatic rings to generate new versatile 2a-methyl-8b-(phenylsulfanyl-1,2a,3,8b-tetrahydro-2H-cyclobuta[c]chromenes.