257861-35-1Relevant articles and documents
An allyltitanium derived from acrolein 1,2-dicyclohexylethylene acetal and (η2-propene)Ti(o-i-Pr)2 as a chiral propionaldehyde homoenolate equivalent that reacts with imines with excellent stereoselectivity. An efficient and practical access to optically active γ-amino carbonyl compounds
Okamoto,Teng,Fujii,Takayama,Sato
, p. 3462 - 3471 (2007/10/03)
A chiral allyltitanium compound 2, prepared in situ by the reaction of optically active acrolein 1,2-dicyclohexylethylene acetal (3) with (η2-propene)Ti(O-i-Pr)2 (1), reacts with a variety of acyclic and cyclic imines 4 in a regiospecific way to afford α-addition products 5 as a mixture of the E- and Z-isomers in good combined yield, where the former is predominant in a ratio of 92: 8 to >95:5. The mixture of (E)- and (Z)-5 and pure (E)-5 which could be isolated in several cases were respectively converted to the corresponding β-amino ester 6 to confirm the absolute configuration and enantiomeric purity. The ee of the newly formed asymmetric center of 5 is more than 78% for the mixture of (E)- and (Z)-5 and more than 96% for pure (E)-5. By taking advantage of the versatility of the vinyl ether moiety in 5, optically active γ-amino aldehydes 8, γ-amino aldehyde acetals 7 and 10, γ-amino acids 9, β-amino esters 6, and pyrrolidinoisoquinolines 12 were readily prepared. In the reaction of 2 with optically active α-silyloxyimine 4n, remarkable double stereodifferentiation was observed; thus, the reaction of 2 derived from (S,S)- or (R,R)-3 provided syn- and anti-5n in a ratio of 55:45 or 0:100, respectively. Meanwhile, the stereochemistry of the product in the reaction of 2 with β-silyloxyimine 4o was controlled mainly by 2. Thus, the reaction of β-silyloxyimine 14 with 2 derived from 1 and (R,R)-3 afforded γ-silyloxyimine 15 with 92% diastereoselectivity, from which 4-amino6-hydroxypentadecanal dimethyl acetal (13), a key intermediate for the synthesis of batzelladine D, was synthesized.
