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Chapter-5
Synthesis of highly substituted pyrroles
The final coupling reaction of 1,4-dicarbonyl compounds with amino side
chain (tert-butyl 2-((4R,6R)-6-(2-aminoethyl)-2,2-dimethyl-1,3-dioxan-4-yl)acetate)
(5) in the presence of acid catalyst under microwave irradiation afford pyrrole
derivatives. For optimization of reaction condition 1,4-dicarbonyl compound (ADD-
01) was react with amino side chain (5) by using various acid catalyst in various
solvents or binary mixture of solvents in conventional method and under microwave
irradiation method. The require reaction time and obtained (%) of yield were
summarized in table-1.
Table-1: Optimization of reaction condition for synthesis of AS-01 in various
conditions
Reaction time and yield (%)
Entry Catalyst Solvents
Conventional MW
Time Yield Time Yield
h (%) min (%)
1 PTSA Toluene 38 68 120 88
2 PTSA Cyclohexane 36 70 110 82
3 PTSA Cyclohexane/THF (9:1) 31 78 90 86
4 PTSA Toluene/THF (9:1) 32 76 96 85
5 MSA Toluene 35 78 112 81
6 MSA Cyclohexane 34 74 100 85
7 MSA Cyclohexane/THF (9:1) 30 80 90 87
8 MSA Toluene/THF (9:1) 30 77 88 82
9 Sulfamic acid Toluene 40 74 140 78
10 Sulfamic acid Cyclohexane 42 76 148 80
11 Sulfamic acid Cyclohexane/THF (9:1) 36 72 125 75
12 Sulfamic acid Toluene/THF (9:1) 35 70 130 75
13 Pivalic acid Toluene 32 85 120 82
14 Pivalic acid Cyclohexane 36 83 105 90
15 Pivalic acid Cyclohexane/THF (9:1) 28 90 75 95
16 Pivalic acid Toluene/THF (9:1) 30 84 82 88
On the basis of our study we found that using pivalic acid and binary solvent
Cyclohexane/THF (9:1) gave an excellent yield in short time (Table-1). Having
optimized condition in our hand,
Department of Chemistry, Saurashtra University, Rajkot-360005 170