Reduction of Nitrile 15b. A solution of 2.32 g of nitrile 15b in 120 ml of hexane was cooled to -70" and 24.6 ml of 1 M DIBAL-H in hexane was added.
The mixture was stirred at -70" for 30 min and at ambient temperature for 5 hr, where upon 2 ml of ethyl formate was added and stirring was continued
for 1 hr. The mixture was poured into saturated ammonium chloride solution and, after
20 min, aqueous sulfuric acid was added and the product was isolated with ether,17b affording 2.31 g (96%) of aldehyde 16b.
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