Reduction of Alcohols

IPNBSH (1) is used in the reduction of alcohols to olefins, allenes and ketones under Mitsunobu reaction conditions (Table 1). Treatment of allylic alcohols with 1 forms olefins with the double-bond transposition. 1 is also used in the reduction of alkynyl alcohols and alkyl alcohols to give allenes and alkanes, respectively. Thermal stability of 1 is higher than that of 2-nitrobenzenesulfonyl hydrazide (NBSH), which has been conventionally used. The reduction using 1 can be performed around 0 °C to rt as compared to that using NBSH having to be carried out within –30 to –15 °C. 1 provided greater flexibility with respect to solvent choice, order of addition, and concentration of substrate and reagent. The reaction would proceed the forming of the diazene via the sulfonyl hydrazine, and subsequent loss of dinitrogen to give the reduction products.

Typical Procedure: Synthesis of (E)-3,7,11-trimethyldodeca-1,6,10-triene (Table 1, Entry 1)
Diethyl azodicarboxylate (74 μL, 0.47 mL) is added dropwise to a mixture of IPNBSH (1, 122 mg, 0.474 mmol), trans,trans-fanesol (0.100 mL, 0.393 mmol) and triphenylphosphine (124 mg, 0.473 mmol) in anhydrous THF (9.0 mL) at 0 °C under an argon atmosphere. After 5 min, the reaction mixture is allowed to warm to 23 °C. After 20 min, a mixture of trifluoroethanol and water (1:1, 4.5 mL) is added to the reaction mixture. After 3 h, the reaction mixture is suspended between diethyl ether (25 mL) and water (25 mL), and the aqueous layer is extracted with diethyl ether. The combined organic layers are dried over anhydrous sodium sulfate, filtered, and concentrated. The residue is purified by flash column chromatography on silica gel (eluent: pentane) to give the desired triene (71 mg, Y. 87 %).