December 2008
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In order to evaluate the relative stability of the mono- methylamine, ꢁ177.01; morpholine, ꢁ323.86 kcal/mol;
adduct 7a and bis-adduct 4a, the net change in energy DE dibenzylamine, ꢁ12.10 kcal/mol) suggests that the bis-
(sum of the energies of products, 4aꢃH2Oꢁsum of the ener- (dibenzylaminomethyl) adduct 4a is the least stable product
gies of reactants, 7aꢃHCHOꢃdibenzylamine) was calcu- when compared with bis(dimethylaminomethyl) adduct 2 and
lated. The DE found to be ꢁ25 kcal/mol. This result suggests bis(morpholinomethyl) adduct 3. The stabilities of bis-
that the formation of the bis-adduct 4a is associated with adducts 2 and 3 are higher by 15 and 27 times respectively
higher state of energy leading to lower stability than the than 4a. Thermodynamically, the mono-adduct 7a is more
mono-adduct 7a. The calculated DE for 4a (ꢁ31.37 favoured over bis-adduct 4a.
kcal/mol) was found to be 5 fold higher than 7a (ꢁ6.27
We were successful in preparing the mono-aminomethyl
kcal/mol) when compared against 1a, suggesting the higher adducts, 3ꢀ-dimethylaminomethyl-4ꢀ-hydroxychalcone 5 and
stability of mono-adduct over the bis-adduct. The relative 3ꢀ-morpholinomethyl-4ꢀ-hydroxychalcone 6 from 4ꢀ-hydroxy-
thermodynamic stabilities of mono and bis-adducts corre- chalcone 1a in 21% and 40% yield respectively, by using the
sponding to various amines e.g., dimethylamine, morpholine reactants (paraformaldehyde, amine, 4ꢀ-hydroxychalcone) in
and dibenzylamines were also accounted for by calculating molar ratios (1 : 1 : 1). The structure of the products was con-
1
the enthalpy change (DH), defined as HproductsꢁHreactants dur- firmed by H-NMR, CHN analyses and IR. The conclusion
ing the chemical transformation. The DH for the forma- drawn from the above results was that using the appropriate
tion of mono-adducts from 1a (dimethylamine, ꢁ176.57 molar ratios of the reactants and reaction condition, bis and
kcal/mol; morpholine, ꢁ326.25 kcal/mol; dibenzylamine, mono-Mannich adducts were obtained for dimethylamine
ꢁ15.03 kcal/mol) and bis-adducts from mono-adducts (di- and morpholine whereas in the case of dibenzylamine, irre-
spective of the molar ratios of the reactants and reaction con-
Table 1. Energy Values of the Mono-Mannich Adducts and Bis-Mannich
Adducts of 4ꢀ-Hydroxychalcone 1a
dition used, only mono-adducts 7 were obtained.
The optimum yields of 7 were obtained using paraformal-
dehyde, dibenzylamine and chalcone in molar ratios (2 : 2 : 1)
E (au)
while the use of molar ratios (1 : 1 : 1) extended the reaction
time substantially accompanied by low yields. To obtain the
best yield, 4ꢀ-hydroxychalcone was added to a previously
heated reaction mixture of dibenzylamine and paraformalde-
hyde in ethanol. Refluxing a mixture of dibenzylamine,
paraformaldehyde and chalcone even in 2 : 2 : 1 molar ratio
Amine
Mono-Mannich adduct
Bis-Mannich adduct
Dimethylamine
Morpholine
Dibenzylamine
5, ꢁ896.82
6, ꢁ1048.59
7a, ꢁ1355.91
2, ꢁ1068.95
3, ꢁ1372.42
4a, ꢁ1987.12
Table 2. 1H- and 13C-NMR Data of Mannich Chalcones (7a—e)
Comp.
1H-NMR (d)
13C-NMR (d)
7a
d: 3.66 (s, 4H, C17-H, C18-H, 2ꢄNCH2), 3.86 (s, 2H, C16-H, NCH2),
6.93—6.91 (d, 1H, C14-H), 7.33—7.27 (m, 6H, C21-H, C22-H,
C23-H, C27-H, C28-H, C29-H), 7.43—7.37 (m, 7H, C3-H, C4-H,
C5-H, C20-H, C24-H, C26-H, C30-H), 7.56—7.53 (d, 1H, C8-H,
Jꢂ15 Hz), 7.65—7.64 (dd, 2H, C2-H, C6-H), 7.83—7.79 (d, 1H,
C7-H, Jꢂ15 Hz), 7.83 (d, 1H, C15-H), 7.92 (dd, 1H, C11-H).
d: 3.66 (s, 4H, C17-H, C18-H, 2ꢄNCH2), 3.85 (s, 2H, C16-H, NCH2),
6.92—6.88 (d, 1H, C14-H), 7.33—7.31 (m, 6H, C21-H, C22-H,
C23-H, C27-H, C28-H, C29-H), 7.41—7.37 (m, 6H, C3-H, C5-H,
C20-H, C24-H, C26-H, C30-H), 7.52—7.49 (d, 1H, C8-H,
Jꢂ15.63 Hz), 7.59—7.57 (d, 2H, C2-H, C6-H), 7.76—7.72
(d, 1H, C7-H, Jꢂ15.64 Hz), 7.82 (d, 1H, C15-H), 7.92—7.90
(dd, 1H, C11-H).
d: 3.66 (s, 4H, C17-H, C18-H, 2ꢄNCH2), 3.85 (s, 2H, C16-H,
NCH2), 3.87 (s, 3H, C-31, OCH3), 6.92—6.90 (d, 1H, C14-H),
6.95—6.94 (d, 2H, C3-H, C5-H), 7.37—7.27 (m, 6H, C21-H,
C22-H, C23-H, C27-H, C28-H, C29-H), 7.40—7.38 (m, 4H,
C20-H, C24-H, C26-H, C30-H), 7.44—7.41 (d, 1H, C8-H,
Jꢂ15.56 Hz), 7.62—7.60 (d, 2H, C2-H, C6-H), 7.79—7.76
(d, 1H, C7-H, Jꢂ15.54 Hz), 7.82 (d, 1H, C15-H), 7.92—7.90
(dd, 1H, C11-H).
d: 188.93 (C9), 162.88 (C13), 144.10 (C7), 136.77 (C19, C25),
135.58 (C1), 130.69 (C11), 130.64 (C15), 130.45 (C10), 130.30
(C3, C5), 129.90 (C20, C24, C26, C30), 129.30 (C21, C23, C27,
C29), 129.16 (C4), 128.72 (C22, C28), 128.30 (C2, C6), 122.58
(C12), 122.31 (C8), 116.42 (C14), 58.34 (C16), 57.06 (C17, C18).
7b
7c
d: 188.58 (C9), 163.01 (C13), 142.59 (C7), 136.71 (C19, C25),
136.51(C1), 134.07 (C4), 130.70 (C11), 130.45 (C15), 130.12 (C10),
129.98 (C3, C5), 129.86 (C20, C24, C26, C30), 129.58 (C21, C23,
C27, C29), 129.17 (C22, 28), 128.33 (C2, C6), 122.70 (C12), 122.64
(C8), 116.46 (C14), 58.34 (C16), 57.04 (C17, C18).
d: 188.99 (C9), 162.65 (C13), 161.86 (C4), 143.95 (C7), 136.80
(C19, C25), 131.69 (C11), 130.45 (C15), 130.36 (C10), 129.99
(C20, C24, C26, C30), 129.16 (C21, C23, C27, C29), 128.28
(C22, C28, C1, C2, C6), 122.50 (C12), 119.97 (C8), 116.34 (C14),
114.77 (C3, C5), 58.33 (C16), 57.08 (C17, C18), 55.80 (C31).
7d
7e
d: 2.41 (s, 3H, C31-H), 3.66 (s, 4H, C17-H, C18-H, 2ꢄNCH2),
3.85 (s, 2H, C16-H, NCH2), 6.93—6.91 (d, 1H, C14-H), 7.24—7.22
(d, 2H, C3-H, C5-H), 7.34—7.32 (m, 6H, C21-H, C22-H, C23-H,
C27-H, C28-H, C29-H), 7.40—7.37 (m, 4H, C20-H, C24-H, C26-H,
C30-H), 7.52—7.49 (d, 1H, C8-H, Jꢂ15.59 Hz), 7.56—7.54
(d, 2H, C2-H, C6-H), 7.83—7.77 (d, 1H, C7-H, Jꢂ15.59 Hz), 7.83
(d, 1H, C15-H), 7.93—7.91 (dd, 1H, C11-H).
d: 3.66 (s, 4H, C15-H, C16-H, 2ꢄNCH2), 3.85 (s, 2H, C14-H, NCH2),
6.93—6.91 (d, 1H, C13-H), 7.10—7.08 (q, 1H, C4-H), 7.41—7.32
(m, 13H, C3-H, C5-H, C7-H, C19-H, C20-H, C21-H, C22-H, C23-H,
C25-H, C26-H, C27-H, C28-H, C29-H ), 7.81 (d, 1H, C14-H),
7.92—7.81 (dd, 1H, C10-H), 7.95—7.92 (d, 1H, C6-H, Jꢂ15.33).
d: 189.02 (C9), 162.76 (C13), 144.20 (C7), 141.13 (C4), 136.79
(C19, C25), 132.83 (C1), 130.64 (C11), 130.41 (C15), 130.05 (C10),
129.99 (C3, C5), 129.17 (C20, C24, C26, C30), 128.76 (C21, C23,
C27, C29), 128.29 (C22, C28, C2, C6), 122.53 (C12), 121.28 (C8),
116.38 (C14), 58.33 (C16), 57.07 (C17, C18), 21.91 (C31).
d: 188.28 (C8), 162.87 (C12), 141.06 (C6), 136.77 (C5), 136.57
(C18, C24), 132.01 (C10), 130.59 (C2), 130.35 (C14), 129.99 (C9),
129.16 (C19, C23, C25, C29), 128.71 (C20, C22, C26, C28), 128.66
(C4), 128.30 (C21, C27, C3), 122.55 (C11), 121.06 (C7), 116.44
(C13), 58.33 (C15), 57.05 (C16, C17).