23 Asymmetric Catalysis and Chromatographic …
485
Table 23.6 H reaction of aldehydes with nitromethane catalyzed by (R)-MOF-7
N
Cu
O
N
O
t-Bu
t-Bu
Ph
Ph
CO 2 H
CO 2 H
HO 2 C
HO 2 C
7
(R)+
CH 3 NO 2
R-CHO
OH
R
NO 2
(R)-MOF-7 (1 mol%)
(R)Entry
R
Yield (%)
Ee (%)
1
n-Bu
98
91
2
cyclohexyl
84
92
3
P h
7 1
9 5
4
2-MeC 6 H 4
83
93
5
2-MeOC 6 H 4
88
98
6
2-BrC 6 H 4
75
93
7
2-NO 2 C 6 H 4
73
91
8
2-furyl
86
93
9
2-pyridyl
98
93
10
1-naphthyl
31
81
11
9-anthracyl
11
45
23.2.7 Diels–Alder Reaction
In 2016, Tanaka et al. [14] prepared novel homochiral biphenol-based (R)-MOF-9 by
the solvothermal reaction of the chiral organic (R)-2,2’-dihydroxy-1,1’-binaphthyl4,4’-dibenzoic acid 9 ligand and Cu(NO 3 ) 2 ·3H 2 O in a mixed solvent (DMF–H 2 O) at
55 °C for 4 days. The MOF crystallized in the trigonal R32 space group (Fig. 23.3).
Synthesized chiral (R)-MOF-9 was found to be an effective asymmetric catalyst in
the Diels–Alder reaction between isoprene and N-ethyl maleimide, with up to 81%
yield and 75% ee. The optimized conditions for the reaction were explored, and it
was found that the best yield was obtained when the reaction was performed at 0°C
for 48 h in EtOAc solvent. The scope of the reaction was investigated with various
N-substituted maleimides with isoprene, and lower reactivity and enantioselectivity
were obtained for bulky substrates because of their weak interactions with chiral
(R)-MOF-9 (Table 23.8).