Selective reductions. 33. Potassium triisopropoxyborohydride as a selective reducing agent in organic synthesis. Reaction with selected organic compounds containing representative functional groups

Abstract

The approximate rate and stoichiometry of the reaction of excess pure potassium triisopropoxyborohydride, KIPBH, with 56 selected compounds containing representative functional groups under standardized conditions (tetrahydrofuran, 0 °C) was examined in order to define the characteristics of the reagent for selective reductions. Primary, secondary, and tertiary alcohols evolve hydrogen partially, even after a long period of time. Phenol also generates partial hydrogen, and the reactions of those amines and thiols studied with the reagent are very slow. Aldehydes and ketones are reduced rapidly and quantitatively to give the corresponding alcohols. Unlike sodium and potassium borohydrides, KIPBH is very stereoselective. 2-Methylcyclohexanone can be reduced to the correspondingly less stable isomer, ds-2-methylcyclohexanol, in a high ratio (91% cis isomer). Cinnamaldehyde is rapidly reduced to cinnamyl alcohol, and further reduction is very slow under these conditions. Anthraquinone is cleanly reduced to 9,10-dihydro-9,10-anthracenediol. Carboxylic acids liberate hydrogen only

Fe-Mediated S–S Bond Cleavage and Its Application in the Synthesis of α-Arylthio Carbonyl Compounds

“…Previously, some of the more common reducing agents such as NaBH 4 , [10] LiAlH 4 , [11] K(i-PrO) 3 BH, [12,13] LiAlH(NR 2 ) 3 , [14] Li(t-BuO) 3 AlH, [15] PPh 3 , [16] P(n-Bu) 3 , [17,18] have been used to reductively cleave the S-S bond. Recently, some metals such as In, [19,20] Sn, [21] La, [22] or some metal halides such as InI, [23] or a combination of samarium and a metal halide such as Sm/NiCl 2 , [24] and Sm/CoCl 2 , [25] were reported to cleave S-S bonds efficiently.…”

“…[5][6][7][8][9] It is well known that diaryl disulfides, which are air-stable, low-toxicity and free of smell, have been in great demand as intermediates to synthesis of organic sulfur compounds. Many approaches for reducing disulfides have been reported.Previously, some of the more common reducing agents such as NaBH 4 , [10] LiAlH 4 , [11] K(i-PrO) 3 BH, [12,13] LiAlH(NR 2 ) 3 , [14] Li(t-BuO) 3 AlH, [15] PPh 3 , [16] P(n-Bu) 3 , [17,18] have been used to reductively cleave the S-S bond. Recently, some metals such as In, [19,20] Sn, [21] La, [22] or some metal halides such as InI, [23] or a combination of samarium and a metal halide such as Sm/NiCl 2 , [24] and Sm/CoCl 2 , [25] were reported to cleave S-S bonds efficiently.…”

Thirty Six Years of Research on the Selective Reduction and Hydroboration

“…28 The reagent behaves as an extremely mild reducing agent, similar to sodium borohydride and lithium tri-tertbutoxyaluminohydride. With the exception of aldehydes, ketones, and disulfides, almost all other organic functional groups are inert toward this reagent.…”

“…[129][130][131][132][133] Furthermore, hydroxy-, alkoxy-, acetoxyand methanesulfonyl-incorporated diisopinocampheylborane derivatives (28)(29)(30)(31)(32)(33) were prepared and their applicability in MPV type reduction was explored.…”

“…As mentioned earlier, diisobutylaluminum derivatives (17)(18)(19)(20)(21)(22)(23) 114, 122,124,125,126,140,[144][145][146][147][148] and diisopinocampheylboron derivatives (25)(26)(27)(28)(29)(30)(31)(32)(33) 132, [135][136][137]140,[149][150][151][152][153] have been applied to the regioselective reduction of α,β-unsaturated aldehydes and ketones. All the derivatives examined can reduce a variety of α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols, except Ipc 2 BOR 135-138, which can only reduce aldehydes but not attack ketones at all.…”