Borohydrides, alkyl

In the presence of added lithium borohydride. Alkyl halides are inert to 9-BBN. Tertiary amides are reduced to alcohols. This reaction follows a course different from that of other organoboranes as shown in equation (I). 

Fluoroalkjiations are frequentiy performed indirectly using tandem reactions. Arenes react with sodium borohydride in trifluoroacetic acid to afford otherwise difficult to obtain l,l,l-trifluoro-2,2-diarylethanes. Presumably sodium borohydride reacts initially with the trifluoroacetic acid to produce the trifluoroacetaldehyde or its equivalent, which rapidly undergoes Friedel-Crafts-type condensation to give an intermediate carbinol. The carbinol further alkylates ben2ene under the reaction conditions giving the observed product. The reaction with stericaHy crowded arenes such as mesitylene and durene... 

Unusual reducing properties can be obtained with borohydride derivatives formed in situ. A variety of reductions have been reported, including hydrogenolysis of carbonyls and alkylation of amines with sodium borohydride in carboxyHc acids such as acetic and trifluoroacetic (38), in which the acyloxyborohydride is the reducing agent. 

Reduction. Quinoline may be reduced rather selectively, depending on the reaction conditions. Raney nickel at 70—100°C and 6—7 MPa (60—70 atm) results in a 70% yield of 1,2,3,4-tetrahydroquinoline (32). Temperatures of 210—270°C produce only a slightly lower yield of decahydroquinoline [2051-28-7]. Catalytic reduction with platinum oxide in strongly acidic solution at ambient temperature and moderate pressure also gives a 70% yield of 5,6,7,8-tetrahydroquinoline [10500-57-9] (33). Further reduction of this material with sodium—ethanol produces 90% of /ra/ j -decahydroquinoline [767-92-0] (34). Reductions of the quinoline heterocycHc ring accompanied by alkylation have been reported (35). Yields vary widely sodium borohydride—acetic acid gives 17% of l,2,3,4-tetrahydro-l-(trifluoromethyl)quinoline [57928-03-7] and 79% of 1,2,3,4-tetrahydro-l-isopropylquinoline [21863-25-2]. This latter compound is obtained in the presence of acetone the use of cyanoborohydride reduces the pyridine ring without alkylation. 

Isoquinoline can be reduced quantitatively over platinum in acidic media to a mixture of i j -decahydroisoquinoline [2744-08-3] and /n j -decahydroisoquinoline [2744-09-4] (32). Hydrogenation with platinum oxide in strong acid, but under mild conditions, selectively reduces the benzene ring and leads to a 90% yield of 5,6,7,8-tetrahydroisoquinoline [36556-06-6] (32,33). Sodium hydride, in dipolar aprotic solvents like hexamethylphosphoric triamide, reduces isoquinoline in quantitative yield to the sodium adduct [81045-34-3] (25) (152). The adduct reacts with acid chlorides or anhydrides to give N-acyl derivatives which are converted to 4-substituted 1,2-dihydroisoquinolines. Sodium borohydride and carboxylic acids combine to provide a one-step reduction—alkylation (35). Sodium cyanoborohydride reduces isoquinoline under similar conditions without N-alkylation to give... 

Isoquinoline also forms Reissert compounds when treated with benzoyl chloride and alkyl cyanide (28), especially under phase-transfer conditions (29). The W-phenylsulfonyl Reissert has been converted to 1-cyanoisoquinoline with sodium borohydride under mild conditions (154). When the AJ-benzoyl-l-alkyl derivative is used, reductive fission occurs and the 1-alkyLisoquinoline is obtained. 

Good yields of phenylarsine [822-65-17, C H As, have been obtained by the reaction of phenylarsenic tetrachloride [29181-03-17, C H AsCl, or phenyldichloroarsine [696-28-6], C3H3ASCI25 with lithium aluminum hydride or lithium borohydride (41). Electrolytic reduction has also been used to convert arsonic acids to primary arsines (42). Another method for preparing primary arsines involves the reaction of arsine with calcium and subsequent addition of an alkyl haUde. Thus methylarsine [593-52-2], CH As, is obtained in 80% yield (43) ... 

Alkylation of enamines with epoxides or acetoxybromoalkanes provided intermediates for cyclic enol ethers (668) and branched chain sugars were obtained by enamine alkylation (669). Sodium enolates of vinylogous amides underwent carbon and nitrogen methylation (570), while vicinal endiamines formed bis-quaternary amonium salts (647). Reactions of enamines with a cyclopropenyl cation gave alkylated imonium products (57/), and 2-benzylidene-3-methylbenzothiazoline was shown to undergo enamine alkylation and acylation (572). A cyclic enamine was alkylated with methylbromoacetate and the product reduced with sodium borohydride to the key intermediate in a synthesis of the quebrachamine skeleton (57i). 

A phenyl ethanol amine in which the nitrogen is alkylated by a long chain alphatic group departs in activity from the prototypes. This agent, suloctidil (43) is described as a peripheral vasodilator endowed with platelet antiaggregatory activity. As with the more classical compounds, preparation proceeds through bromination of the substituted propiophen-one ( ) and displacement of halogen with octyl amine. Reduction, in this case by means of sodium borohydride affords suloctidil (43). ... 

Schiff s base (j ) derived by reaction of p-chloro-anil ine and borohydride followed by acylation with phenylacetyl chloride produces amide 22,. Selective hydrolysis with HBr followed by alkylation with isopropyl bromide completes the synthesis of lorcainide (20). ... 

Friedel-Crafts alkylation of 8-hydroxycarbostyrils, such as leads to substitution at the C-5 position, namely, In this case an a-haloacyl reagent is employed. Displacement with isopropylamine and careful sodium borohydride reduction (care is... 

The key intermediate 21 is in principle accessible in any of several ways. Thus reaction of thiophenecarbox-aldehyde with amninoacetal would lead to the Schiff base 20 treatment with acid would result in formation of the fused thiophene-pyridine ring (21). Alkylation of that intermediate with benzyl chloride gives the corresponding ternary imini urn salt 23. Treatment with sodium borohydride leads to reduction of the quinolinium ring and thus formation of ticlopidine (24). ... 

Condensation of piperazine with 2-methoxytropone gives the addition-elimination product 12 [2]. Alkylation of the remaining secondary amino group with bromoketone 13, itself the product from acylation of dimethyl catechol, gives aminoketone 14. Reduction of the carbonyl group with sodium borohydride leads to secondaiy alcohols 15 and 16. Resolution of these two enantiomers was achieved by recrystallization of their tartrate salts to give ciladopa (16) [3],... 

The synthesis of the E-ring intermediate 20 commences with the methyl ester of enantiomerically pure L-serine hydrochloride (22) (see Scheme 9). The primary amino group of 22 can be alkylated in a straightforward manner by treatment with acetaldehyde, followed by reduction of the intermediate imine with sodium borohydride (see 22 —> 51). The primary hydroxyl and secondary amino groups in 51 are affixed to adjacent carbon atoms. By virtue of this close spatial relationship, it seemed reasonable to expect that the simultaneous protection of these two functions in the form of an oxazolidi-none ring could be achieved. Indeed, treatment of 51 with l,l -car-bonyldiimidazole in refluxing acetonitrile, followed by partial reduction of the methoxycarbonyl function with one equivalent of Dibal-H provides oxazolidinone aldehyde 52. 

The oxo group of 9a is reduced by sodium borohydride to the corresponding alcohol, which can be dehydrated with /Moluenesulfonic acid. Subsequent alkylation with dimethyl sulfate and potassium im-butoxide gives the 5-methoxy-substituted 1-benzothiepin 13 in 45 % yield.90... 

The enantiomerically pure chloromethyl complexes (-)-(/ )-9 and ( + )-(S)-9 (shown below as 10) can be converted to iron-alkyl complexes by treatment with sodium borohydride, Grignard reagents, or alkyllithium species, with no loss of enantiomeric purity16,17 (see also Houben-Weyl, Vol. 13/9 a, p 193). 

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