89036-90-8Relevant academic research and scientific papers
Diastereoselection during 1,2-Addition of the Allylindium Reagent to α-Thia and α-Amino Aldehydes in Aqueous and Organic Solvents
Paquette, Leo A.,Mitzel, Thomas M.,Isaac, Methvin B.,Crasto, Curtis F.,Schomer, William W.
, p. 4293 - 4301 (2007/10/03)
The stereochemistry of the indium-promoted reaction of allyl bromide with α-thia (PhS and MeS), disubstituted α-amino (Bn2N, Me2N, isoindolyl), and protected α-amino aldehydes (Ac and Boc) in water has been evaluated. The reactions involving the sulfur derivatives are minimally diastereoselective, indicating that the allylindium reagent is not thiophilic. Chelation is not observed and π-facial discrimination is achieved via Felkin - Ahn transition states under the steric control of the substituents. The Garner aldehyde is also anti-diastereoselective. Interestingly, N-acetylmannosamine is appreciably responsive to chelation control and is capable of generating 90% of the syn β-amino alcohol when reacted in a 0.5 M NH4Cl solution. While the α-dibenzylamino substituent is too bulky to enter into complexation, the α-dimethylamino group is not and can lead to high levels (99%) of syn diastereomer. The size of other neighboring substituents does have an impact on π-facial discrimination in these systems and can erode the stereoselectivity accordingly.
Additive Pummerer reactions of vinylic sulfoxides. Synthesis of γ-hydroxy-α,β-unsaturated esters, α-hydroxyketones, and 2-phenylsulfenyl aldehydes and primary alcohols
Craig, Donald,Daniels, Kevin,MacKenzie, A. Roderick
, p. 11263 - 11304 (2007/10/02)
Treatment of β-monosubstituted vinylic sulfoxides 1 with trifluoroacetic anhydride in dichloromethane gave excellent yields of 1,2-bis(trifluoroacetoxy)thioethers 6. Mildly basic methanolysis of 2-alkyl-substituted 6 gave α-hydroxyaldehydes 11 as monomer-dimer mixtures; similar treatment of the 2-aryl analogues afforded aryl (hydroxymethyl) ketones 12. Compounds 11 underwent Wittig reactions with methoxycarbonylmethylenetriphenylphosphorane to give high yields of γ-hydroxy-α,β-unsaturated esters 13, predominantly as the E-isomers. β-Monosubstituted vinylic sulfoxides 1 possessing a β-aryl group, and β-disubstituted vinylic sulfoxides 3 reacted with trifluoromethanesulfonic anhydride-sodium acetate in acetic anhydride to give 2-(phenylsulfenyl) acylals 14. These gave 2-phenylsulfenyl aldehydes 15 upon basic methanolysis, and the corresponding primary alcohols 16 on reduction with sodium borohydride. Reaction of both geometric isomers of enantiomerically pure vinylic sulfoxide 1o with TFAA gave racemic 6o as a mixture of diastereomers. Reaction of optically pure (E)- and (Z)-1p with trifluoromethanesulfonic anhydride-sodium acetate in acetic anhydride gave acylal 19 in 10.5 and 23% e.e., respectively.
Chelation and non-chelation controlled stereoselective reduction of a-methoxy-a-phenylthio ketones
Annunziata,Cinquini,Cozzi,Fuchicello
, p. 3853 - 3868 (2007/10/02)
A series of a-methoxy-a-phenylthio substituted ketones bearing an additional stereocenter in a1-position was prepared, and the reduction with chelating and non chelating reagents was studied. 'Internal matched' pairs (leading to highly stereoselective pro
Mechanistic Insight into Allylmetal-Thioacetal Reactions Employing 2-Acetoxy-2-phenylacetaldehyde Thioacetals
Sato, Tsuneo,Otera, Junzo,Nozaki, Hitosi
, p. 6116 - 6121 (2007/10/02)
The mechanism of allyl-metal-thioacetal reactions has been investigated by using 2-acetoxy-2-phenylacetaldehyde thioacetals in the presence of trimethylsilyl triflate.The results unambiguously revealed the occurence of both SN1- and SN/su
