CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

General procedure for Barbier type allylation/crotylation of 1 in H 2 O or THF. Finely
divided metal powder (In, Sb, Ga or Bi) was added to a mixture of 1 (5.0 g, 0.029 mol) and
allyl /crotyl bromide (equivalents specified in Table III.2.1 and Table III.2.2) in H 2 O (30
mL) or THF (30 mL). After stirring the mixture for the time specified in Table III.2.1 and
Table III.2.2, it was filtered and worked-up as above to isolate the pure products. For the
reaction with Sb, an aqueous solution of KF (5-6 mL, 2M) was also added in the reaction
mixture. The In-mediated reaction was also carried out in the presence of LiCl and KI (1.0
equiv. each).
Procedure for allylation/crotylation in [bmim][Br]. A mixture of the metal (In, Ga or
Bi) and allyl/crotyl bromide (quantities specified in Table III.2.1 and Table III.2.2) in
[bmim][Br] (3 mL/mmol) was stirred at room temperature for 0.5 h, followed by addition
of the aldehyde 1. The reaction mixture was stirred at room temperature for 4-5 h. After
completion of the reaction (cf. TLC), the mixture was extracted with Et 2 O (30 mL), the
ether extract evaporated in vacuo and the residue purified by column chromatography
(silica gel, 0-15% EtOAc/hexane) to give the respective products as colourless oils.
Crotylation of 1 via the Grignard route. To a stirred solution of 1 (1.70 g, 0.01 mol) in
THF (25 mL) was slowly injected the Grignard reagent [prepared from crotyl bromide
(4.10 g, 0.03 mol) and Mg-turnings (1.20 g, 0.05 mol)] in Et 2 O or THF (40 mL). After
stirring for 12 h, the reaction was quenched with aqueous saturated NH 4 Cl (2 mL). The
organic layer was separated and the aqueous portion extracted with Et 2 O (30 mL). The
combined organic extracts were washed with brine (5 mL), and dried. Solvent removal in
vacuo and column chromatography of the residue afforded the pure homoallylic alcohols
69a-c.
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