CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

O
O
3
CHO
i
O
O
+
OH
13a
O
O
OH
O
O
OH
13b
+ O
O
OH
+
O
O
OH
+
O
O
OH
7a. R = CH 3
9a. R = C 6 H 13
7b. R = CH 3 7c. R = CH 3 7d. R = CH 3
9b. R = C 6 H 13 9c. R = C 6 H 13 9d. R = C 6 H 13
i) Allyl bromide/g-alkylated allyl bromide, metal (Mg/Sb/In/Ga/Bi), solvent (H 2 O/THF/[bmim][Br])
Scheme 6
The In-mediated allylation (Scheme 6, Table 5) produced best yield (78%) of the
allylated products (13a/b) in [bmim][Br], while excellent syn:anti diastereoselectivity
(2:98) was achieved in THF. Surprisingly, Ga was ineffective in THF and proceeded with
modest yield and diastereoselectivity` in H 2 O.
Table 5. Reaction course of allylation of 3 using different metals in different solvents a
Entry
Allyl
Metal
Solvent Additive Time (h) Yield
13a:13b c
bromide
(equiv.)
(%)
(equiv.)
1 4 In (2.5) H 2 O -- 5 58 24.2 : 75.8
2 3.5 In (2.5) THF KI + LiCl 7 69 2.0 : 98.0
3 1.2 In (1.0) [bmim][Br] -- 3 78 29.8 : 70.2
4 4 Ga (2.5) H 2 O -- 6 48 21.9 : 78.1
5 3.5 Ga (2.5) THF KI + LiCl 16 NR --
6 1.2 Ga (1.0) [Bmim][Br] -- 4 73 5.0 : 95.0
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