Topics in Current Chemistry (2019) 377:23
1 3
the cationic scandium metal center was proposed to promote the reaction. The
TRIP group of ligands (S)-L5 in complex with Ca/Sc constitute a well-defined
chiral environment that tunes the orbital-favored and less-space-demanding endo
transition state (Scheme 34).
In 2014, Luo and co-workers developed a new intermolecular azo-transfer
of aryl triazenes 132 with 1,3-dicarbonyl compounds under Sc(OTf) 3 catalysis
(Scheme 35) [137]. The combination of Sc(III)-activated triazenes 133 and enol
ether species 132 completed a conjugate addition and a N–N bond cleavage providing aliphatic azo compounds 131 with good yields and wide substrate scopes.
However, an initial catalytic asymmetric variant with (R)-L20 showed a disappointing ee value (24% ee).
Scheme 34 Asymmetric binary acid-catalyzed [4 + 2] cycloadditions with simple olefins
Scheme 35 Sc(OTf) 3 -catalyzed transfer diazenylation of dicarbonyl compounds with triazenes
Reprinted from the journal
178
1 3
the cationic scandium metal center was proposed to promote the reaction. The
TRIP group of ligands (S)-L5 in complex with Ca/Sc constitute a well-defined
chiral environment that tunes the orbital-favored and less-space-demanding endo
transition state (Scheme 34).
In 2014, Luo and co-workers developed a new intermolecular azo-transfer
of aryl triazenes 132 with 1,3-dicarbonyl compounds under Sc(OTf) 3 catalysis
(Scheme 35) [137]. The combination of Sc(III)-activated triazenes 133 and enol
ether species 132 completed a conjugate addition and a N–N bond cleavage providing aliphatic azo compounds 131 with good yields and wide substrate scopes.
However, an initial catalytic asymmetric variant with (R)-L20 showed a disappointing ee value (24% ee).
Scheme 34 Asymmetric binary acid-catalyzed [4 + 2] cycloadditions with simple olefins
Scheme 35 Sc(OTf) 3 -catalyzed transfer diazenylation of dicarbonyl compounds with triazenes
Reprinted from the journal
178