Effect of ligand on ring contraction of six-membered nickel-containing cyclic esters, LnNiCH2CH2CH2COO, to their five-membered-ring isomers, LnNiCH(CH3)CH2COO. Kinetic and thermodynamic control of asymmetric induction by chiral diphosphines in the ring contraction

1987 ◽  
Vol 109 (4) ◽  
pp. 1092-1100 ◽  
Author(s):  
Takakazu Yamamoto ◽  
Kenji Sano ◽  
Akio Yamamoto
Keyword(s):  
Membered Ring ◽  
Asymmetric Induction ◽  
Thermodynamic Control ◽  
Ring Contraction ◽  
Cyclic Esters

ChemInform Abstract: [3,3]-Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven-Membered-Ring Carbamates and Ring Contraction to Pyrrolidines.

ChemInform ◽  
2016 ◽  
Vol 47 (21) ◽  
Author(s):  
Aurelie Mace ◽  
Sabrina Touchet ◽  
Patricia Andres ◽  
Fernando Cossio ◽  
Vincent Dorcet ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

Untersuchungen zur Ringkontraktion am 1,4-Dithia-2,6-diaza-3,5-diborinan-System/ Studies on Ring Contraction of the l,4-Dithia-2,6-diaza-3,5-diborinane System

1988 ◽  
Vol 43 (8) ◽  
pp. 959-962 ◽  
Author(s):  
Carl Habben ◽  
Anton Meiler ◽  
Stefan Pusch
Keyword(s):  
Mass Spectra ◽  
Ring System ◽  
Membered Ring ◽  
Ring Contraction ◽  
C Nmr

AbstractThe 1,4-dithia-2,6-diaza-3,5-diborinanes 1a-d react with elemental sodium with formation of the 1,3-diaza-2,4-diboretidines 2a-d. By use of more sodium in case of 1 d or 3,5-bis(diethylamino)- 2-cyclohexyl-6-trimethylsilyldiborinane, the 1,3-thiaza-2,4-diboretidines 3 were formed. 3.5-Dimethyl-2,6-bis(trimethylsilyl)-1,4-dithia-2,6-diaza-3,5-diborinane gives the borazine 4, The reaction of di-t-butyl-sulfurdiimide with 2,6-di-t-butyl-3,5-dimethyl-1,4-dithia-2,6-diaza-3,5-diborinane leads by ring contraction to the four-membered ring system 5. 1H, 11B, 13C NMR and mass spectra are reported and discussed.

[3,3]-Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven-Membered-Ring Carbamates and Ring Contraction to Pyrrolidines

2015 ◽  
Vol 55 (3) ◽  
pp. 1025-1029 ◽  
Author(s):  
Aurélie Macé ◽  
Sabrina Touchet ◽  
Patricia Andres ◽  
Fernando Cossío ◽  
Vincent Dorcet ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

Hypervalent-Iodine-Mediated Ring-Contraction Monofluorination Affording Monofluorinated Five-Membered Ring-Fused Oxazolines

2017 ◽  
Vol 19 (19) ◽  
pp. 5300-5303 ◽  
Author(s):  
Yong-Chao Han ◽  
Yan-Dong Zhang ◽  
Qun Jia ◽  
Jian Cui ◽  
Chi Zhang
Keyword(s):  
Membered Ring ◽  
Hypervalent Iodine ◽  
Ring Contraction

[3,3]-Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven-Membered-Ring Carbamates and Ring Contraction to Pyrrolidines

2015 ◽  
Vol 128 (3) ◽  
pp. 1037-1041 ◽  
Author(s):  
Aurélie Macé ◽  
Sabrina Touchet ◽  
Patricia Andres ◽  
Fernando Cossío ◽  
Vincent Dorcet ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

Stereoselective and enantioselective synthesis of five-membered rings via conjugate additions of allylsulfone carbanions

2000 ◽  
Vol 72 (9) ◽  
pp. 1671-1683 ◽  
Author(s):  
Alfred Hassner ◽  
Eugene Ghera ◽  
Tamar Yechezkel ◽  
Victoria Kleiman ◽  
Thiagarajan Balasubramanian ◽  
...  
Keyword(s):  
Membered Ring ◽  
Optically Active ◽  
Enantioselective Synthesis ◽  
Ring Closure ◽  
Chiral Auxiliary ◽  
Asymmetric Induction ◽  
Conjugate Additions ◽  
Derivatives Of ◽  
The Michael Addition ◽  
High Stereoselectivity

This lecture describes some of our studies of lithio derivatives of allyl sulfone carbanions which add α-regioselectively as well as anti diastereoselectively to Michael acceptor olefins. This can be ascribed to chelation in the Michael addition step. When the reaction leads to subsequent ring closure by using a bromoallyl sulfone, the latter acts as a methylenemethane synthon in a (3+2) Michael-initiated ring closure, affording highly functionalized cyclopentane derivatives. Such additions proceed with high stereoselectivity and with asymmetric induction leading to nonracemic substituted cyclopentanones. Additions of allyl sulfone carbanions also proceed stereoselectively to C=N systems containing a chiral auxiliary on N. These can be used in the synthesis of optically active five- and six-membered ring N-heterocycles. Furthermore, chiral groups on the allyl sulfone moiety can induce significant remote asymmetric induction, made possible by the presence of an aromatic π-system which promotes intramolecular chelation to the Li cation.

scholarly journals 1,3-Asymmetric Induction in Diastereoselective Allylations of Chiral N-Tosyl Imines

2021 ◽  
Author(s):  
Jared Shaw ◽  
Anna Lo ◽  
David Gutierrez ◽  
Garrett Toth-Williams ◽  
James Fettinger
Keyword(s):  
Transition State ◽  
Bioactive Compounds ◽  
Lewis Acid ◽  
Amino Alcohols ◽  
Membered Ring ◽  
Asymmetric Induction ◽  
Stereoelectronic Interactions ◽  
Transition State Structures

Lewis-acid mediated allylations of β-alkoxy N-tosyl imines lead to 3-alkoxy homoallylic N-tosyl amines with anti diastereoselectivity. Diastereoselectivity and yields of reactions are comparable between two methods of Hosomi-Sakurai allylations. Observed selectivity trends and computational evidence suggest that 1,3 asymmetric induction occurs through the formation of a six- membered ring chelate which adopts a half-chair-like conformation. The product ratios of allylations to β-alkoxy N-tosyl imines are dependent on conformation preferences of the chelate and stereoelectronic interactions in the transition-state structures. Debenzylation and detosylation of these allylation products result in anti 1,3-amino alcohols, a privileged motif in synthetic and natural bioactive compounds.

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