Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Amino alcohols, alkynic cyclization

A diastereoselective formal addition of a 7ra i-2-(phenylthio)vmyl moiety to a-hydroxyhydrazones through a radical pathway is shown in Scheme 2.29. To overcome the lack of a viable intermolecular vinyl radical addition to C=N double bonds, not to mention a reaction proceeding with stereocontrol, this procedure employs a temporary silicon tether, which is used to hold the alkyne unit in place so that the vinyl radical addition could proceed intramolecularly. Thus, intermolecular addition of PhS" to the alkyne moiety in the chiral alkyne 161 leads to vinyl radical 163, which cyclizes in a 5-exo fashion, according to the Beckwith-Houk predictions, to give aminyl radical 164 with an a 7z-arrangement between the ether and the amino group. Radical reduction and removal of the silicon tether without prior isolation of the end product of the radical cyclization cascade, 165, yields the a-amino alcohol 162. This strategy, which could also be applied to the diastereoselective synthesis of polyhydroxylated amines (not shown), can be considered as synthetic equivalent of an acetaldehyde Mannich reaction with acyclic stereocontrol. [Pg.33]

The organolanthanide-catalyzed alkene hydroamination has been reported. With this approach, amino alkenes (not enamines) can be cyclized to form cyclic amines, and amino alkynes lead to cyclic imine. The use of synthesized C-1 and C-2 symmetric chiral organolanthanide complexes give the amino alcohol with good enantioselectivity. [Pg.1181]


See other pages where Amino alcohols, alkynic cyclization is mentioned: [Pg.30]    [Pg.150]    [Pg.375]    [Pg.503]    [Pg.20]    [Pg.340]    [Pg.162]    [Pg.540]    [Pg.335]    [Pg.356]    [Pg.247]    [Pg.410]    [Pg.61]    [Pg.102]   
See also in sourсe #XX -- [ Pg.769 ]

See also in sourсe #XX -- [ Pg.5 , Pg.769 ]

See also in sourсe #XX -- [ Pg.769 ]

See also in sourсe #XX -- [ Pg.5 , Pg.769 ]




SEARCH



Alcohols amino alcohol

Alkynals, cyclization

Alkyne-Alcohols

Alkyne-alcohols => alkynes

Alkynes cyclizations

Alkynic alcohols

Alkynic alcohols cyclization

Amino alcohols

Amino alcohols, alkynic

Amino cyclization

Cyclization alkynes

© 2024 chempedia.info