Sodium Boranate Research Articles

Iminium-functionalized 1,2,3-triazoles by [3+2] cycloaddition reactions of internal acetylenic iminium triflates with organoazides

Abstract Propyne iminium triflates 1–6 react as dipolarophiles in thermal [3 + 2]-cycloadditions with sufficiently electron rich organoazides to form 1,4,5-trisubstituted 1,2,3-triazoles with iminium functionalization. The reactions require rather strong thermal activation, but can be accelerated by microwave irradiation. The regioselectivity of the cycloaddition at the internal acetylenic bond of 3-cyclopropylpropyne and 3-arylpropyne iminium ions (1–3 and 4, respectively) is very high, but is lowered in the presence of sterically demanding substituents at the opposite end of the iminium-substituted C,C triple bond. The iminium-functionalized triazoles can easily be transformed into neutral compounds; herein reported is the formation of triazolyl ketones 10 by hydrolysis and of tertiary triazolyldimethyl amines 12 by LiAlH4 reduction. When the reduction is performed with sodium boranate or sodium cyanoboranate, amine–borane complexes 15 and 16 are obtained.

Development of Effective Cobalt Catalysts for Hydrogen-Generating Solid Phase Compositions Based on Sodium Borane

Hydrogen-generating solid phase compositions based on sodium boran are promising systems for storage and transportation of hydrogen to be used for low-temperature fuel cells with proton-exchange membranes. Catalysts are added to the compositions in order to generate hydrogen at ambient temperature. The studies were focused on the influence of conditions of the cobalt catalysts preparation on the rate of gasgeneration. The efficiency of hydrogen evolution depended on the nature of the cobalt salt and pH of its aqueous solution where the active component precursor was reduced under the action of the hydride; these factors determined the composition, dispersion and magnetic behavior of the cobalt systems. The maximal rate of gas generation (505 cm 3 /min per 1 g of the composition containing 8.4 wt % of hydrogen) was observed in the presence of the sample reduced by sodium borane in a cobalt chloride solution with pH 1.3. The results obtained can be used to develop effective and inexpensive cobalt catalysts for generation of hydrogen from solid compositions based on sodium borane.

ChemInform Abstract: An Improved Method for the Preparation of Desoxopeptides. Reductions of Endothiopeptides.

AbstractDiprotected dipeptides such as (I) are converted to the corresponding endothiopeptides such as (III), which undergoes reduction with nickel boride, generated in situ from sodium boranate and nickel chloride hexahydrate, to form the deoxopeptide (IV).

ChemInform Abstract: Synthesis and Reductions of cis‐ and trans‐1,4,4a,6,7,8,9,11a‐Octahydropyrido(2,1‐b)quinazolin‐11‐one.

Abstractcis‐2‐Amino‐4‐cyclohexenecarboxylic acid (I) undergoes cyclocondensation with O‐methyl‐δ‐valerolactim (II) to give the cis‐fused octahydropyridoquinazolinone (III) which is hydrogenated with sodium boranate or catalytically to form the tricyclic compounds (IV) or (V).

ChemInform Abstract: Reduction of Isophorone with Sodium Borohydride: Change in Regioselectivity with Hydrotropes.

AbstractIsophorone (I) is subjected to reduction with sodium boranate in an alkaline aqueous medium.

ChemInform Abstract: Selective Hydrogenolysis of 3,5‐Disubstituted Functionalized 2‐Isoxazolines.

AbstractReduction of the isoxazolines (I) with sodium boranate in the presence of nickel(II) sulfate proceeds under ring opening and hydrogenation of the double bond in the side chain to give predominantly the amino alcohols (II).

ChemInform Abstract: 2,2‐Dimethyl‐5‐(5‐R‐2‐furfurylidene)‐1,3‐dioxane‐4,6‐diones. Part 4. Synthesis, Structure, and Properties of Thiophene Analogues.

AbstractThe thiophenealdehydes (I) react with Meldrum's acid (II) to give the thienylmethylene compounds (III) which are reduced with sodium boranate, forming the thenyl derivatives (IV).

ChemInform Abstract: Asymmetric Synthesis. Part 18. Preparation of Chiral 1,2‐Diamines via the CN (R,S) Method. Application to the Synthesis of an Analogue of Tetraponerine.

AbstractThe cyanoperhydrooxazolopyridine (I) reacts with butyllithium (IIa) or lithium dibutylcuprate (IIb) to give the imine (III) which is reductively cleaved with sodium boranate to yield the diamino carbinol (IV).

ChemInform Abstract: Synthesis of Novel 3‐Formamido‐3‐(acylamino)monobactams.

AbstractThe 4‐(methylsulfonyl)azetidinone (I) is desulfonated with sodium boranate, detritylated with p‐toluenesulfonic acid monohydrate and then coupled with p‐nitrobenzaldehyde (III) to form the imine (IV).

ChemInform Abstract: Tris(trimethylsilyl)silane: A Catalyst for Radical‐Mediated Reduction Reactions.

AbstractThe silane (II), generated in situ from the silyl halides (I) by reduction with sodium boranate, is employed in the reductive dehalogenation of the halides (III), yielding the hydrocarbons (IV).

Properties of 5-Hydroxyvalerate CoA-Transferase fromClostridium aminovalericum

5-Hydroxyvalerate CoA-transferase from Clostridium aminovalericum, strain T2-7, was purified approximately 100-fold to homogeneity. The molecular mass of the native enzyme was determined by three different methods to be 178 +/- 11 kDa; that of the subunit was 47 kDa, indicating a homotetrameric structure. The following CoA esters acted as substrates (decreasing specificity, V/Km): 5-hydroxyvaleryl-CoA greater than propionyl-CoA greater than acetyl-CoA greater than (Z)-5-hydroxy-2-pentenoyl-CoA greater than butyryl-CoA greater than valeryl-CoA. 4-Pentenoate and 3-pentenoate were also activated by acetyl-CoA to the corresponding CoA esters, whereas crotonate, (E)-5-hydroxy-2-pentenoate, (E)-2-pentenoate and 2,4-pentadienoate were not attacked. 5-Hydroxyvalerate CoA-transferase showed ping-pong kinetics and was inactivated by sodium boranate only in the presence of a CoA substrate. This indicated the formation of a thiolester between a specific carboxyl group of the enzyme and CoASH during the course of the reaction. The CoA-transferase was inhibited by ATP and CTP, slightly by ADP, GTP and UTP, but not by AMP. The inhibition by ATP was competitive towards CoA esters and noncompetitive towards acetate.

ChemInform Abstract: Synthesis of Amines by Reduction of Imines with the MCl2/NaBH4 (M = Co, Ni) System.

AbstractThe imines (I) and (III) are treated with sodium boranate and cobalt dichloride in methanol/THF, producing the corresponding amines (II) or (IV).

ChemInform Abstract: Synthesis of (R)‐(‐)‐ and (2R,3R)‐(‐)‐(2‐2H)Mevalonolactone.

AbstractThe epoxide (I), synthesized from geraniol, is converted into the key intermediate (VIII) which produces the diol (IX) on ozonolysis and reduction with sodium boranate.

ChemInform Abstract: Chemoselective Reductions with Sodium Borohydride. Aldehydes vs. Ketones.

AbstractWhen mixtures of the aldehydes (I) with the ketones (II) are treated with sodium boranate in ethanol/methylene chloride, the aldehydes (I) are selectively reduced to give the primary alcohols (III).

ChemInform Abstract: Dihydro‐5,6‐imidazo(2,1‐b)thiazoles, Dihydro‐2,3‐imidazo(2,1‐b)benzothiazoles, Analogues of Levamisole.

AbstractThe 2‐aminobenzothiazoles (I) are alkylated with the bromomethyl ketones (II) to form the iminium salts (III) which are reduced with sodium boranate, yielding the hydroxy compounds (IV).

ChemInform Abstract: Organophosphorus Chemistry. Part 2. The Reduction of Quinquevalent Phosphorus to the Trivalent State.

AbstractThe phosphorochloridates (I) are treated with a dispersion of sodium boranate in dioxane to give the phosphorous acid diesters (II).

ChemInform Abstract: Sodium Borohydride Desulfurization of Thiolactams to Amines.

AbstractReductive desulfurization of the thiolactams (Ia), (II), and (IV) with sodium boranate yields the amines (Ib), (III), and (V).

ChemInform Abstract: Novel Reactions of the Low Valent Cobalt Reagent Generated Using CoCl2 and NaBH4/C2H5OH in the Presence of Carbon Monoxide.

AbstractReaction of the terminal olefin (I) with sodium boranate, CoCl2 (II), and carbon monoxide (III) proceeds via the complex (IV) which yields either the alkane (V) or the rearranged E‐alkene (VI) depending on the method of work‐up.

ChemInform Abstract: Reduction of α,β‐Unsaturated Nitroalkenes with Borane and Borohydrides. A Convenient Route to 3‐Nitro‐, 3‐Hydroxylamino‐, and 3‐Amino‐2H‐1‐benzopyran Derivatives.

AbstractThe nitrochromenes (I) and (III) are reduced using sodium boranate to give the trans‐3‐nitrochromones (II) and (IV).

ChemInform Abstract: Synthesis and Reaction of Dibenzoyl Ditelluride.

AbstractSodium hydrogen telluride (II), prepared from tellurium (I) and sodium boranate, reacts with benzoyl chloride (IV) to give dibenzoyl ditelluride (VI) via the telluride (V).