Cyclo- and hydrodimerization of α,β-unsaturated ketones promoted by samarium diiodide

A New Cyclopentanol as a Side Product in the Reduction of the Chalcone : Şalkonun Redüksi̇yonunda Bi̇r Yan Ürün Olarak Yeni̇ Bi̇r Si̇klopentanol

“…This stereochemical preference is explained by the fact that during the initial step of cyclodimerization, an electron is transferred from metal to the chalcone to afford a radical enolate, which then attacks the chalcone to form carbon-carbon bond. At this stage, an anti-position, which minimizes the steric interactions, is favored for both the radical anion and chalcone, thus allowing the phenyl groups at C-3 and C-4 to adopt trans dispositions [7]. The relative configurations at the remaining carbons of the cyclopentanol are such that 1-hydroxyl, 2-carbonyl and 4-phenyl substituents are on the same face, whereas 1-phenyl and 3-phenyl are on the opposite face.…”

“…However, in many cases, the 3,4-trans configuration is reported to be the major product [6,7,9,10]. This stereochemical preference is explained by the fact that during the initial step of cyclodimerization, an electron is transferred from metal to the chalcone to afford a radical enolate, which then attacks the chalcone to form carbon-carbon bond.…”

“…On the other hand, at certain conditions, cx,Punsaturated ketones can also undergo an intermolecular aldol reaction with Zn, Sm, In, Sn, Nd metals to afford cyclopentanol derivatives [6][7][8][9][10][11]. The configurations of these cyclodimerization products may vary at C-3 and C-4 as being trans or cis, depending on the reaction conditions and the reagents utilized in the C-5,C-2,C=0,C-2"",C-6""…”

“…It has been amply documented in literature that the intramolecular cycloreductive coupling of a,|3-unsaturated ketones in the presence of metals such as Yb, Zn, Nd, Sn, In, Sm yield cyclopentanol derivatives in high yields [6,7]. Since it is also known that similar reductions with different reagents and reaction conditions result in cyclopentanols with either cis or trans configurations at C-3 and C-4 [6][7][8][9] stereochemical preferences of 3 were established by using NMR data.…”

Cyclodimerization of α,β–α′,β′‐unsaturated ketones promoted by samarium diiodide. Complete assignment of the 1H and 13C NMR spectra of hydroxycyclopentylpropenone derivatives

“…In a previous paper we reported that the reaction of˛,ˇ-unsaturated ketones with the SmI 2 -hexamethylphosphoramide (HMPA)-tetrahydrofuran (THF) system led to the formation of cyclopentanol derivatives in good yields. 3 In those studies, the x-ray structures of the cyclodimers were determined and showed that the reaction was stereocontrolled and that only two of 16 possible stereoisomers were obtained. This led us to study the influence of various substituents on the stereochemistry of the final products.…”