Chemistry Reference
In-Depth Information
5 mol %
i-Pr
i-Pr
N
Ar
Me
Kinetic resolution
O
Mo
O
Ph
Oi-Pr
O
Me
Oi-Pr
B
Ar
Me
OH
Me
O
B
i-PrO
3a
C;
remove i-PrOH
C
6
H
6
, 22
°
Me
Me
Ar = 2,4,6-i-Pr
3
C
6
H
2
C
6
H
6
, 22
°
C, 80 min
O
i
-Pr
OH
B
Me
O
H
H
2
O
2
Me
O
NaOH
H
Me
Me
k
rel
> 25, 37% yield
Mo-catalyzed desymmetrization products
Representative functionalization
Oi-Pr
O
Me
O
H
HO
B
Ph
OH
O
O
H
OO
OH
Me
Me
Me
Toluene, 80
°
C, 12 h
Me
OH
Me
Me
68% yield
>98% de, >98% ee
38% yield, >98% ee
58% yield, >98% ee
>98% ee
Scheme 8E.5.
Mo-catalyzed enantioselective RCM of allylboronates: one-pot net enantioselective
cross - metathesis.
enantioselectivity, including chiral tertiary alcohols. (3) A direct CM of allyl alcohol with
any Mo or Ru catalyst would be diffi cult to achieve due to facile catalyst decomposition
[17]. (4) In addition to oxidation, the chiral cyclic allylboronates can be used as crotylat-
ing reagents, providing the desired diols in good yield and high diastereoselectivity.
8E.2.3. Synthesis of Bicyclic Lactams and Cyclic Amines through Mo-Catalyzed
Enantioselective RCM
Small- and medium-ring N-containing heterocycles are prevalent in biologically active
molecules [18]; the development of catalytic enantioselective synthesis of azacycles thus
constitutes an important objective in chemical synthesis. Enantioselective synthesis of
N-containing compounds by catalytic olefi n metathesis was fi rst reported in 2002 [19];
in all such reactions, however, substrates contain an N-aryl group to reduce the possibil-
ity that the Lewis basic heteroatom may cause diminution of the catalytic activity of the
chiral Mo complex [20]. Since access to enantiomerically enriched cyclic amines consti-
tutes an important objective in organic synthesis, and because the removal of N-aryl
