Anomalous threo-diastereoselectivity in allylic silane- or stannane–aldehyde condensation reactions: new interpretation of the antiperiplanar vs. synclinal problem on the transition-state conformations
Unusual threo-diastereoselectivity has been observed in the intermolecular reactions of β-substituted crotyl-silane or-stannane with 2-benzyloxypropanal under chelation conditions, which implies preference for the synclinal over the antiperiplanar transition state.
Comparative Diastereoselectivity Analysis of Crotylindium and 3-Bromoallylindium Additions to α-Oxy Aldehydes in Aqueous and Nonaqueous Solvent Systems
作者:Leo A. Paquette、Thomas M. Mitzel
DOI:10.1021/jo9613489
日期:1996.1.1
The couplings of crotyl bromide (1) and 1,3-dibromopropene (2) to a triad of conformationally unrestricted a-oxy aldehydes in water, aqueous THF (1:1), and anhydrous THF are described. In no example involving 1 was the formation of anti,syn product detected. The proportion of syn isomers reached a maximum (syn/anti = 5.6:1) when the neighboring hydroxyl group was unprotected and water was the reaction medium. Although internal chelation also operates to some degree with 2, considerable erosion of this mechanistic pathway (maximum now only 2:1) in favor of Felkin and ''anti-Felkin'' transition states is reflected in the product distributions. This trend can be synthetically advantageous, and a utilitarian example is demonstrated. The indium reagents studied here are notably efficient nucleophilic reaction partners in water.
Chiral synthesis via organoboranes. 21. Allyl- and crotylboration of .alpha.-chiral aldehydes with diisopinocampheylboron as the chiral auxiliary
作者:Herbert C. Brown、Krishna S. Bhat、Ramnarayan S. Randad
DOI:10.1021/jo00268a017
日期:1989.3
Allylcopper Intermediates with N-Heterocyclic Carbene Ligands: Synthesis, Structure, and Catalysis
作者:Vincenzo Russo、Jessica R. Herron、Zachary T. Ball
DOI:10.1021/ol902458v
日期:2010.1.15
Allylcopper intermediates with N-heterocyclic carbene ligands are synthesized by transmetalation of allylsiloxane reagents, and the crystal structures of allylcopper compounds are reported. The allylcopper transmetalation is utilized for catalytic aldehyde allylation, which is found to be facilitated by a trifluorosilane co-catalyst.
BROWN, HERBERT C.;BHAT, KRISHNA S.;RANDAD, RAMNARAYAN S., J. ORG. CHEM., 54,(1989) N, C. 1570-1576
作者:BROWN, HERBERT C.、BHAT, KRISHNA S.、RANDAD, RAMNARAYAN S.