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Dihydroisoquinolines borohydride reduction

The isoquinoline system is conveniently prepared from treatment of o-iodobenzylamines with the enolate ions derived from symmetrical ketones (or ketones with one a-position blocked), aldehydes, or the dimethyl acetal of pyruvaldehyde, to give aminocarbonyl compounds which condensed in situ to give 2- and/or 3-substituted 1,2-dihydroisoquinolines. Catalytic dehydrogenation or borohydride reduction of these products then led to the corresponding isoquinolines or tetrahydroisoquinolines in moderate to high... [Pg.478]

Treatment of the compounds 78 with various alkyl halides in the presence of sodium hydride results in 1-alkylation as with normal Reissert com-pounds. ° Acylation has also been reported under these conditions. Under a variety of conditions, however, 78 does not react with benzaldehyde. Acid hydrolysis of 80 gave tetrahydroquinaldic acid, while acid hydrolysis of the alkylated dihydroisoquinoline-Reissert compounds gave the amino acids 81. By first complexing the alkylated dihydroisoquinoline-Reissert compound with zinc chloride in ether and then hydrolyzing the complex, the nitrile was hydrolyzed to an acid, but the amide group was left intact. The perchlorate salts of dihydroisoquinoline-Reissert compounds have also been prepared, and sodium borohydride reduction proceeds in the same manner as reduction of the Reissert salt to... [Pg.207]

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... [Pg.396]

Nucleophilic addition takes place at C-1, and this is considerably enhanced if the reaction is carried out upon an isoquinolinium salt. Reduction with lithium aluminium hydride [tetrahydroaluminate(III)] in THF (tetrahydrofuran), for example, gives a 1,2-dihydroisoquinoline (Scheme 3.15). These products behave as cyclic enamines and if isoquinolinium salts are reacted with sodium borohydride [tetrahy-droboronate(III)] in aqueous ethanol, further reduction to 1,2,3,4-tetrahydroisoquinolines is effected through protonation at C-4 and then hydride transfer from the reagent to C-3. [Pg.51]

The reduction of isoquinolinium ions has been extensively investigated with borohydride and aluminum hydride ions. The use of boro-hydride ion in a protonic solvent normally leads to the formation of 1,2,3,4-tetrahydroisoquinolines, whereas the reduction with aluminum hydride ion in an aprotic medium generally gives a 1,2-dihydroiso-quinoline. This 1,2-dihydroisoquinoline contains an enamine system and may undergo further reaction on treatment with acid. The 1,2-and 3,4-dihydroisoquinolines as well as isoquinolinium ions are reduced by the borohydride ion in a protonic medium to the 1,2,3,4-tetrahydroisoquinolines. [Pg.68]

The reduction of 2-substituted-isoquinolinium salts has been reported by Torossian65 with potassium borohydride in water, by Mirza,68 and by Durmand et al.,87,68 using sodium borohydride in aqueous methanol to yield 1,2,3,4-tetrahydroisoquinolines. The reduction of the second double bond appears to arise from a mechanism similar to that leading to tetrahydropyridines from pyridinium ions (see Section I). Mirza66 (see also Bose60) found that the reduction of berberine (60) with sodium borohydride could be stopped at the 1,2-dihydro-intermediate (61), and Karrer and Brook70 showed that the 1,2-dihydroisoquinoline formed by the lithium aluminum hydride reduction of l-phenyl-2-methylisoquinolinium iodide (62) could be further reduced to the 1,2,3,4-tetrahydroisoquinoline (63) with sodium borohydride in methanol. Awe et al.71,72 and Huffman73... [Pg.69]

The tetrahydroisoquinolone (1), iV-methylcorydaldine, has been isolated from Papaver bracteatum,6 and it is apparently a true constituent, not an artefact. The (+)-(i )- and (-)-(5)-forms of salsolidine (2) have been prepared by the reduction with sodium borohydride of the dihydroisoquinolines [3 R = (+)-(i )-PhCHMe, (-MS)-PhCHMe, (—)-(S)-PhCHEt, or (-)-(S)-C10H7CHMe] (which were prepared in three steps from 3,4-dimethoxyphenylacetaldehyde and RNH2) followed by hydrogenolysis over 10% Pd(OH)2 on carbon.7... [Pg.87]

Chiral sodium acyloxy borohydride 554 prepared from NaBH4 and AyV-phthaloyl amino acid reduced cyclic imines in good enantioselectivity. Thiazazincolidine complex 555 was shown to be an excellent catalyst for the catalytic reduction of dihydroisoquinolines with BH3-THF (Equation (265)).1132-1134... [Pg.227]

Thiazoles are deactivated towards electrophilic substitution, and thus direct reaction with hydride re-ductants to give thiazolines should be facilitated. There are indeed some examples of this type of reaction, but it is more common to reduce N-alkylated thiazolium salts (209). These compounds are converted first by reaction with sodium borohydride into 4-thiazolines (210), which in protic solvents become protonated and undergo further reduction to yield thiazolidines (211). Similarly the isoquinoli-nium salt (213), formed by the acid-promoted cyclization of the isoquinoline (212), is converted into the tetrahydroisoquinoline (214) (presumably via an intermediate 1,2-dihydroisoquinoline) by reaction with sodium borohydride. ... [Pg.656]

Lithium in liquid ammonia conditions can produce l,4-dihydroquinoline" and 3,4-dihydroisoquinoline." Conversely, lithium aluminium hydride reduces generating l,2-dihydroquinoline" and 1,2-dihydroisoquinoline. These dihydro-heterocycles can be easily oxidised back to the fully aromatic systems, or disproportionate, especially in acid solution, to give a mixture of tetrahydro and re-aromatised compounds. Stable dihydro-derivatives (see also 9.13) can be obtained by trapping following reduction, as a urethane, by reaction with a chloroformate. Quaternary salts of quinoline and isoquinoline are particularly easily reduced, either catalyticaUy or with a borohydride in protic solution, giving... [Pg.183]

A shorter and neater synthesis of (+ )-dihydrogambirtannine involved the multiple-phase reduction of the isoquinolinium salt 78 with sodium borohydride in a methanol-ether—water system in the presence of a high concentration of cyanide ion. The intermediate, presumably the cyanide (79) formed by trapping of the initially generated dihydroisoquinoline derivative by nucleophilic cyanide ion, was not isolated but was converted directly into ( )-dihydrogambirtannine (67) by heating in dilute hydrochloric acid. Dehydrogenation of the stable hydrochloride of 67 by means of iodine and sodium acetate afforded an improved route... [Pg.147]

Isolaudanosoline is the name given by Franck and Blaschke (196) to the tetraphenolic base CXXXIV (R = H). The tetramethyl derivative (CXXXIV R = CH3) [mp 76°-77° B HCI, 139°-141°] was prepared by Livshits et al. (197) who employed the Bischler-Napieralski reaction although they obtained instead of the usual dihydroisoquinoline base (CXXXV R = H2) the ketone CXXXV (R = O) whose methiodide on reduction afforded CXXXIV (R = CH3). In the absence of oxygen the dihydro base CXXXV (R = H2) can be prepared directly and its methiodide on reduction with sodium borohydride yields CXXXIV (R = CH3) [oil picrate, mp 189°]. When the methiodide of the latter base (CXXXVI R = CH3) was demethylated with hydrobromic acid the methobromide of isolaudanosoline was obtained (CXXXVI R = H). Its oxidation in aqueous solution with ferric chloride afforded an aporphine base (CXXXVII) [chloride, mp 225°-228° bromide, mp 170°-174°]... [Pg.441]


See other pages where Dihydroisoquinolines borohydride reduction is mentioned: [Pg.14]    [Pg.72]    [Pg.221]    [Pg.70]    [Pg.75]    [Pg.72]    [Pg.16]    [Pg.318]    [Pg.450]    [Pg.197]    [Pg.224]    [Pg.327]   
See also in sourсe #XX -- [ Pg.69 , Pg.75 ]




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1.2- Dihydroisoquinolines reduction

3.4- dihydroisoquinoline

Borohydride reductions

Reduction borohydrides

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