Iron(III) Chloride-Sodium Hydride1


[7705-08-0]  · Cl3Fe  · Iron(III) Chloride-Sodium Hydride  · (MW 162.20) (NaH)

[7646-69-7]  · HNa  · Iron(III) Chloride-Sodium Hydride  · (MW 24.00)

(mild reduction of aldehydes and ketones to alcohols;2 reduction of alkenes and alkynes3)

Alternate Name: ferric chloride-sodium hydride.

Preparative Method: generated in situ via addition of a solution of Iron(III) Chloride (14 mg equiv) in THF (20 mL) to a suspension of Sodium Hydride (42 mg equiv) in THF (5 mL). The yellow suspension is stirred at rt for 4 h under argon. A solution of the carbonyl compound (2 mmol) in THF (2 mL) is added and stirring continued at rt.

Handling, Storage, and Precautions: FeCl3 is hygroscopic and corrosive; inhalation or ingestion may be fatal. NaH is a flammable solid which reacts violently with water. The powder ignites spontaneously in air. It should be handled in an inert dry atmosphere. Use in a fume hood.

Reduction of Carbonyl Compounds.2

FeCl3-NaH is one of a class of reagents called complex reducing agents (CRA), which essentially lower the basicity of NaH. An iron hydride species is assumed to be the active component. A mixture of FeCl3 and NaH in a 1:3 ratio produces the best results for reductions of aldehydes and ketones to alcohols in good yields (75-85%) (eqs 1 and 2). A related reagent, NaH-Zinc Chloride-Chlorotrimethylsilane, reduces a variety of aldehydes and ketones in good yield (81-100%).4 FeCl2-NaH also reduces carbonyl compounds to alcohols, but in lower yields.2

Reduction of Alkenes and Alkynes.3

Double and triple bonds of aliphatic and aromatic alkenes and alkynes, are reduced to alkanes with FeCl3 or Iron(II) Chloride in THF (eq 3). Enones can be reduced to the corresponding saturated alcohol (eq 4). An alternate reagent NaH-t-BuONa-FeCl3 represents a viable alternative for this reduction as it requires fewer equivalents of CRA and is selective. Also it does not reduce aldehydes or ketones.5 Many combinations of these reagents containing different metal salts and sodium alkoxides have been developed for reduction of organohalides and alkenes/alkynes to alkanes.1,5,6 The metal hydrides NaH, Potassium Hydride, and LiH in combination with n-Butyllithium-N,N,N,N-Tetramethylethylenediamine or t-BuONa-TMEDA have been used as metallating and reducing agents.7

The combinations of FeCl3-Lithium Aluminum Hydride8 to reduce alkenes to alkanes and FeCl3-BuLi to deoxygenate epoxides to alkenes9 are of related interest.

1. Caubere, P. AG(E) 1983, 22, 559.
2. Fujisawa, T.; Sugimoto, K.; Ohta, H. JOC 1976, 41, 1667.
3. Fujisawa, T.; Sugimoto, K. CL 1976, 581.
4. Nordahl, A.; Carlson, R. ACS 1990, 44, 274.
5. Brunet, J. J.; Caubere, P. TL 1977, 3947.
6. (a) Brunet, J. J.; Mordenti, L.; Loubinoux, B.; Caubere, P. TL 1977, 1069. (b) Loubinoux, B.; Vanderesse, R.; Caubere, P. TL 1977, 3951.
7. Pi, R.; Friedel, T.; von Rague Schleyer, P. JOC 1987, 52, 4299.
8. Ashby, E. C.; Lin, J. J. TL 1977, 4481.
9. Fujisawa, T.; Sugimoto, K.; Ohta, H. CL 1974, 883.

Andrew D. White

Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA

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