CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

was treated with excess amount of benzyl bromide, metal salts (CuCl 2 , 2H 2 O or FeCl 3 ) and
metal to ensure the progress of the successful ones at faster rate.
BrCH 2 Ph + M BrMCH 2 Ph
RCHO + BrMCH 2 Ph
89a-g
R
OH
CH 2 Ph
90a-g
O
1
O
CHO
+ BrMCH 2 Ph
O
91a
O
OH
Ph
+
O
O
91b
OH
Ph
Scheme III.1.9
The combination of Zn and metal salts were ineffective for the benzylation of all
the aldehydes 89a-g. Likewise, the combination of FeCl 3 /Mg system also did not give the
desired products with any of these aldehydes. However, using a combination of Mg and
CuCl 2 .2H 2 O, the benzylation of the aldehydes 89a-g proceeded smoothly to furnish the
corresponding homobenzylic alcohols 90a-g in modest to good yields (58-74%) (Table
III.1.5). The reaction was comparatively faster (7-9h) with the aromatic aldehydes, while
the aliphatic substrates reacted sluggishly (16-18h). The homobenzyl alcohols were
characterized from their IR peak at ~3400 cm -1 (-OH group), the 1 H NMR peaks at δ 3.0-
3.3 ppm [-CH(OH)] and multiplet at δ 7.2-8.0 ppm (-Ph) and as well as the 13 C NMR
peaks at δ ~45 ppm (benzylic carbon). As a representative example, 1 H and 13 C NMR
spectra of 90e are shown in Fig. III.1.20 and Fig. III.1.21 respectively.
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