Regio- and Stereochemistry on the Electrophilic Trapping of Allylic Samariums Generated by Reductive Cleavage of Allylic Ethers with (C₅Me₅)₂Sm(thf)_n

Abstract

The C−O bond of allylic benzyl ethers was selectively cleaved with Cp*2Sm(thf) n to give allylic samarium complexes in good yields. Facility of their bond fission has been found to be comparable to that of the corresponding propargylic ethers intermolecularly, but lower intramolecularly. Regio- and stereochemistry on the electrophilic trapping of the allylic complexes thus generated remarkably depended on the nature of the electrophiles. They reacted with carbonyl compounds exclusively from the most substituted terminus of the allylic moieties to yield blanched homoallylic alcohols with anti diasteroselectivity. On the other hand, trapping with silyl chlorides produced linear allylic silanes. Here, a plausible mechanism to account for the difference is proposed.

Gallium-mediated allyl transfer from bulky homoallyl alcohol to aldehydes or alkynes: Control of dynamic σ-allylgalliums based on retro-allylation reaction

“…The following compounds were characterized according to the literature: 2a [11], 2b [12], 2c [11], 2d [11], 2e [13], 2f [11], 2h [14], 2i [15], 2j [15], 2k-m [11], 2n [16], 2o [14], 2p [17], 2q [17], 6b [18], 6f [18], 6g [18], 6g-d 2 [19], 6g-d 1 [20], 6i [18], and 6n [21]. d 14.34, 15.09, 16.39, 22.89, 29.35, 29.38, 29.40, 29.50, 29.65, 32.10, 32.51, 43.88, 44.83, 76.21, 76.54, 115.86, 116.59, 130.21, 130.63, 133.57.…”

Regioselective 1,4‐Silylcupration of 1,3‐Dienes — Characterization and Electrophilic Trapping of the Intermediate (σ‐Allyl)copper Complex.

“…The identity of some products was proven by comparison with published spectroscopic data: 8a, [30] 8b, [31] 9a, [32] 9b, [33] 10a [2c] , 11a [33] , 11b [2c] , 27. [34] …”

Highly Diastereoselective Construction of Acyclic Systems with Two Adjacent Quaternary Stereocenters by Allylation of Ketones

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Diastereoselective construction of acyclic systems bearing multiple stereogenic centers is one of the most challenging areas in organic synthesis. Recently much attention has been paid to diastereoselective allylation of ketones with various g-monosubstituted allylmetals such as organoboron, [2] silicon, [3] tin, [4] zinc, [5] titanium, [6] indium, [7] vanadium, [8] and samarium [9] species. Recently much attention has been paid to diastereoselective allylation of ketones with various g-monosubstituted allylmetals such as organoboron, [2] silicon, [3] tin, [4] zinc, [5] titanium, [6] indium, [7] vanadium, [8] and samarium [9] species.

…”

“…[1] Reaction of allylmetals with unsymmetrical carbonyl compounds is a major approach to this challenge. Recently much attention has been paid to diastereoselective allylation of ketones with various g-monosubstituted allylmetals such as organoboron, [2] silicon, [3] tin, [4] zinc, [5] titanium, [6] indium, [7] vanadium, [8] and samarium [9] species. A much more arduous task is the stereoselective construction of acyclic systems having two adjacent quaternary carbon atoms, and only most recently highly stereoselective construction of such systems by the allylation of ketones has been achieved by Knochel and co-workers [10] and Marek and co-workers [11] using g,g-disubstituted allylzinc reagents.…”