Synthetic Applications of the β-Lithiation of β-Aryl Secondary Amides: Diastereoselective and Enantioselective Substitutions
摘要:
The sequence of beta-lithiation and electrophilic substitution of beta-aryl secondary amides is reported. The lithiations occur regioselectively at the beta-position, and the resulting lithiated intermediates can be reacted with a wide range of electrophiles to give substituted products. Reactions of beta-lithiated amides bearing an alpha-substituent provide substituted products with high diastereoselectivity, Electrophilic substitutions of beta-lithiated N-methylamides in the presence of the chiral diamine (-)-sparteine provide highly enantioenriched products. The methodology is used to synthesize enantioenriched beta-aryl beta-substituted amides, acids, and lactones.
Reaction of arylboronreagents, arylboronic acids or arylborates, which are readily accessible by lithiation of aryl bromides followed by treatment with trimethoxyborane, with α,β-unsaturated esters in the presence of rhodium/(S)-binap catalyst proceeded with high enantioselectivity to give high yields of optically active β-aryl esters of up to 98% ee. The enantioselectivity depends on the steric bulkiness
Dispiroketals in synthesis (Part 16): Functionalised dispiroketals as new chiral auxiliaries; the synthesis of dihydroxylated dispiroketals in optically pure form and their application as bifunctional, C2-symmetrical, chiral auxiliaries for highly stereos
作者:Barend C. B. Bezuidenhoudt、Grant H. Castle、Jean E. Innes、Steven V. Ley
DOI:10.1002/recl.19951140410
日期:——
A range of rigid, architecturally complex diols derived from dispiroketals have been synthesised. A bifunctional, C2-symmetrical, chiralauxiliary derived from these dihydroxylateddispiroketals has been used to induce a high degree of asymmetry in Michael additions of cuprates to a variety of di-α, β-unsaturated ester systems.
A FACILE ASYMMETRIC SYNTHESIS OF β-SUBSTITUTED ALKANOIC ACID THE HIGHLY STEREOSELECTIVE MICHAEL ADDITION OF GRIGNARD REAGENTS TO α,β-UNSATURATED CARBOXYLIC AMIDES DERIVED FROM L-EPHEDRINE
作者:Teruaki Mukaiyama、Nobuharu Iwasawa
DOI:10.1246/cl.1981.913
日期:1981.7.5
The Michael addition of Grignard reagents to chiral α,β-unsaturated carboxylic amides derivedfrom 1-ephedrine affords highly optically active β-substituted alkanoic acids after acid hydrolysis. This high stereoselectivity is explained by considering the formation of rigid internal chelate complexes.
Dispiroketals in synthesis (Part 14): Functionalised dispiroketals as new chiral auxiliaries; highly stereoselective Michael additions to a bifunctional, C2- symmetrical chiral auxiliary
作者:Grant H. Castle、Steven V. Ley
DOI:10.1016/0040-4039(94)85340-1
日期:1994.10
A bifunctional, C2-symmetricalchiralauxiliary derived from dihydroxylateddispiroketals has been used to induce a high degree of asymmetry in Michael additions of cuprates to a variety of di-α,β-unsaturated ester systems.
Asymmetric conjugate addition reaction by the use of ()-γ-trityloxymethyl-γ-butyrolactam as a chiral auxiliary
作者:Kiyoshi Tomioka、Toshiro Suenaga、Kenji Koga
DOI:10.1016/s0040-4039(00)84021-6
日期:1986.1
(S)-γ-Trityloxymethyl-γ-butyrolactam (2) serves as a chiralauxiliary in the conjugate addition reaction of the corresponding imide (3) of α,β-unsaturated carboxylic acids with Grignard reagents in the presence of CuBrSMe2 in THF to give, after hydrolysis, the β,β-disubstituted carboxylic acids (5) with predictable absolute configuration and high enantiomeric excess.