Lithium cyanoborohydride

Consequently, by choosing proper conditions, especially the ratios of the carbonyl compound to the amino compound, very good yields of the desired amines can be obtained [322, 953]. In catalytic hydrogenations alkylation of amines was also achieved by alcohols under the conditions when they may be dehydrogenated to the carbonyl compounds [803]. The reaction of aldehydes and ketones with ammonia and amines in the presence of hydrogen is carried out on catalysts platinum oxide [957], nickel [803, 958] or Raney nickel [956, 959,960]. Yields range from low (23-35%) to very high (93%). An alternative route is the use of complex borohydrides sodium borohydride [954], lithium cyanoborohydride [955] and sodium cyanoborohydride [103] in aqueous-alcoholic solutions of pH 5-8. 

Lithium cyanoborohydride reduces oximes to hydroxylamines in good yield. Careful pH control is not necessary in this case and reduction can be done efficiently in the presence of acetic acid at pH 5 . Lithium borohydride reduces oximes as well. Sodium borohydride in acetic acid or on silica gel has been used for reduction of oximes, but reported yields were low to moderate only. Lithium aluminum hydride " and DIBAL are capable of reducing oximes, but are sufficiently chemoselective for reduction of polyfunctional oximes. 

The reducing agents employed include hydrogen and a catalyst (such as nickel) or NaBHsCN or LiBHsCN (sodium or lithium cyanoborohydride). The latter two reducing agents are similar to NaBH4 and are especially effective in reductive aminations. Three specific examples of reductive amination foUow ... 

This method (Scheme 23) was proposed in 1974 by Ahmad (144) who used excess lithium cyanoborohydride as the reducing agent, a-Oximino acids (80) or equimolar quantities of a-keto acid and hydrox-ylamine were reduced at pH 5 in aqueous solution. This procedure was also successfully applied to the synthesis of N-hydroxytyrosine (35) (95) (Scheme 23). 

The substitution of hydride ligands in [BH ] and [A1H4]" anions by other groups is an effective approach to the modification of the reducing abilities of these reagents. Many substituted hydrides have been synthesized by replacement of H- in the [BH4] anion. For example, alkali metal trialkylborohydrides and trialkoxyborohydrides, as well as sodium and lithium cyanoborohydrides O" and dicyanoborohydrides, 2,l5 been... 

The 8-methyl-8,14-cycloberbine 364, derived from the protoberberine 324 via the betaine 363, was reduced with sodium borohydride or lithium aluminum tri-tert-butoxyhydride to give a diastereoisomeric mixture of cis-and trans-alcohols (7.8 1 or 1 7.8, respectively) (Scheme 64).t)n exposure to formaldehyde the mixture underwent N-hydroxymethylation and subsequent intramolecular substitution on the aziridine ring to give the oxazolidine 365. Removal of the hydroxyl group in 365 was accomplished by chlorination followed by hydrogenolysis with tributyltin hydride. Reductive opening of the oxazolidine 366 with sodium cyanoborohydride afforded ( )-raddeanamine (360), which has already been converted to ochotensimine (282) by dehydration. 

Replacement of hydrogen by alkyl groups gives compounds like lithium triethylborohydride (Super-Hydride ) [100], lithium tris sec-butyl)borohydride [101] (L-Selectride ) and potassium tris sec-butyl)borohydride (K-Selectride ) [702], Replacement by a cyano group yields sodium cyanoborohydride [103], a compound stable even at low pH (down to 3), and tetrabutylammonium cyanoborohydride [93],... 

Opening of a bottle where some particles of lithium aluminum hydride were squeezed between the neck and the stopper caused a fire [68]. Lithium aluminum hydride must not be crushed in a porcelain mortar with a pestle. Fire and even explosion may result from contact of lithium aluminum hydride with small amounts of water or moisture. Sodium bis(2-methoxy-ethoxy)aluminum hydride (Vitride, Red-Al ) delivered in benzene or toluene solutions also may ignite in contact with water. Borane (diborane) ignites in contact with air and is therefore kept in solutions in tetrahydrofuran or in complexes with amines and sulfides. Powdered lithium borohydride may ignite in moist air. Sodium borohydride and sodium cyanoborohydride, on the other hand, are considered safe. ... 

The double bond in indole and its homologs and derivatives is reduced easily and selectively by catalytic hydrogenation over platinum oxide in ethanol and fluoroboric acid [456], by sodium borohydride [457], by sodium cyanoborohydride [457], by borane [458,459], by sodium in ammonia [460], by lithium [461] and by zinc [462]. Reduction with sodium borohydride in acetic acid can result in alkylation on nitrogen giving JV-ethylindoline [457]. 

Chemical reduction of aromatic aldehydes to alcohols was accomplished with lithium aluminum hydride [5i], alane [770], lithium borohydride [750], sodium borohydride [757], sodium trimethoxyborohydride [99], tetrabutylam-monium borohydride [777], tetrabutylammonium cyanoborohydride [757], B-3-pinanyl-9-borabicyclo[3.3.1]nonane [709], tributylstannane [756], diphenylstan-nane [114], sodium dithionite [262], isopropyl alcohol [755], formaldehyde (crossed Cannizzaro reaction) [i7i] and others. 

Transformation of ketones to alcohols has been accomplished by many hydrides and complex hydrides by lithium aluminum hydride [55], by magnesium aluminum hydride [89], by lithium tris tert-butoxy)aluminum hydride [575], by dichloroalane prepared from lithium aluminum hydride and aluminum chloride [816], by lithium borohydride [750], by lithium triethylboro-hydride [100], by sodium borohydride [751,817], by sodium trimethoxyborohy-dride [99], by tetrabutylammonium borohydride [771] and cyanoborohydride [757], by chiral diisopinocampheylborane (yields 72-78%, optical purity 13-37%) [575], by dibutyl- and diphenylstannane [114], tributylstanrume [756] and others Procedure 21, p. 209). 

Reduction of unsaturated ketones to unsaturated alcohols is best carried out Nit v complex hydrides. a,/3-Unsaturated ketones may suifer reduction even at the conjugated double bond [764, 879]. Usually only the carbonyl group is reduced, especially if the inverse technique is applied. Such reductions are accomplished in high yields with lithium aluminum hydride [879, 880, 881, 882], with lithium trimethoxyaluminum hydride [764], with alane [879], with diisobutylalane [883], with lithium butylborohydride [884], with sodium boro-hydride [75/], with sodium cyanoborohydride [780, 885] with 9-borabicyclo [3.3.1]nonane (9-BBN) [764] and with isopropyl alcohol and aluminum isopro-... 

Hydrazones treated with alkalis decompose to nitrogen and hydrocarbons [845, 923] Woljf-Kizhner reduction) (p. 34), and p-toluenesulfonylhydra-zones are reduced to hydrocarbons by lithium aluminum hydride [812], sodium borohydride [785] or sodium cyanoborohydride [813]. Titanium trichloride hy-drogenolyzes the nitrogen-nitrogen bond in phenylhydrazones and forms amines and ketimines which are hydrolyzed to the parent ketones. Thus 2,4-dinitrophenylhydrazone of cycloheptanone afforded cycloheptanone in 90% yield [202]. 

Thioamides were converted to aldehydes by cautious desulfurization with Raney nickel [1137, 1138] or by treatment with iron and acetic acid [172]. More intensive desulfurization with Raney nickel [1139], electroreduction [172], and reduction with lithium aluminum hydride [1138], with sodium borohydride [1140] or with sodium cyanoborohydride [1140] gave amines in good to excellent yields. 

Reduction of 3-aryl-4-oxo-4//-pyrido[2,l-fl]phthalazine-l-carboxamides with sodium cyanoborohydride in acidified methanol or lithium borohy-dride in tetrahydrofuran afforded 6,7-dihydro derivatives 47 (R = H) (88EUP294599). 

Using boron-based reagents Chlorodiisopinocampheylborane, 72 Lithium triethylborohydride, 205 Sodium cyanoborohydride-Tin(II) chloride, 280... 

Tributyltin hydride, 316 Zinc iodide, 280 From alkyl halides Lithium aluminum hydride-Ceri-um(III) chloride, 159 Palladium catalysts, 230 Sodium cyanoborohydride-Tin(II) chloride, 280 From alkyl sulfonates Lithium triethylborohydride, 153 From thiols... 

From carbonyl groups Sodium cyanoborohydride-Zinc iodide, 280 From thioketals Lithium aluminum hydride-Bis-(cyclopentadienyl)nickel, 158 From arenesulfonylhydrazones Sodium borohydride, 278 Sodium cyanoborohydride-Zinc iodide, 280... 

Anyway, MADAM-6 is not active. And the equally intriguing positional isomer, the easily made MADAM-2, will certainly contribute to these speculations. A quiz for the reader Will 2,N-dimethyl-3,4-methylenedioxyamphetamine (MADAM-2) be (1) Of much reduced activity, akin to MADAM-6, or (2) Of potency and action similar to that of MDMA, or (3) Something unexpected and unanticipated I know only one way of finding out. Make the Schiffs base between piperonal and cyclohexylamine, treat this with butyl lithium in hexane with some TMEDA present, add someN-methylformanilide, convert theformed benzaldehyde toanitrostyrenewith nitroethane, reduce this with elemental iron to thephenylacetone, reduce this in the presence of methylamine with sodium cyanoborohydride, then taste the result. 

EXTENSIONS AND COMMENTARY There are about twenty different synthetic routes in the literature for the preparation of MDA. Many start with piperonal, and employ it to make methylenedioxyphenylacetone or a mcthylcnedioxydihydro-cinnamic acid amide instead of the nitrostyrene. The phenylacetone can be reduced in several ways other than the cyanoborohydride method mentioned here, and the amide can be rearranged directly to MDA. And there are additional methods for the reduction of the nitrostyrene that use no lithium aluminum hydride. Also there are procedures that have safrole or isosafrole as starting points. There is even one in the underground literature that starts with sassafras root bark. In fact, it is because safrole is one of the ten essential oils that MDA can humorously be referred to as one of the Ten Essential Amphetamines. See the comments under TMA. 

In other reports, /i-cyclodcxtrins have been used to induce asymmetry in borohydride reduction of ketones,166 a diastereoselective reduction has been controlled167 by a real lyltricarbonyl iron lactone tether , a phosphinamide has been combined with a dioxaborolidine unit as an activated, directed catalyst for ketone reduction,168 reductive amination using benzylamine-cyanoborohydride converts 3-hydroxy ketones into syn-1,3-amino alcohols,169 l-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propan-l-one has been reduced diastereoselectively,170 and production of chiral alcohols via (i) Itsuno-Corey and Brown procedures171 and (ii) lithium aluminium hydride modified by chiral nucleophiles172 has been reviewed. 

This rationalization indicates that internal delivery of a hydride is not a requisite for the observed stereospecificity. Reduction of the oxonium ion with an external hydride reagent should also give equatorially oriented bicyclic ether only. Accordingly (112), reduction of tricyclic spiroketal 145 with sodium cyanoborohydride at pH =3-4 yields only the equatorial bicyclic ether alcohol (J47, CHO=CH2OH). Eliel and co-workers (113) have previously suggested that the orientation of the electron pairs of oxygen atoms influence the course of the reduction of 2-alkoxytetrahydropyran with lithium aluminium hydride-aluminium trichloride. 

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