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Dihydropyridines stereoselectivity

In Diels-Alder reactions a nitroolefin may function as an electron-deficient ene com-onent or a 1,2-dihydropyridine derivative may be used as a diene component. Both types of iactants often yield cyclic amine precursors in highly stereoselective manner (R.K. Hill, 1962 i. BOchi, 1965, 1966A). [Pg.297]

Alkyl-1,4-dihydropyridines on reaction with peracids undergo either extensive decomposition or biomimetic oxidation to A-alkylpyridinum salts (98JOC10001). However, A-methoxycarbonyl derivatives of 1,4- and 1,2-dihydro-pyridines (74) and (8a) react with m-CPBA to give the methyl tmns-2- 2>-chlorobenzoyloxy)-3-hydroxy-1,2,3,4-tetrahydropyridine-l-carboxylate (75) and methyl rran.s-2-(3-chlorobenzoyloxy)-3-hydroxy-l,2,3,6-tetrahydropyridine-l-carboxylate (76) in 65% and 66% yield, respectively (nonbiomimetic oxidation). The reaction is related to the interaction of peracids with enol ethers and involves the initial formation of an aminoepoxide, which is opened in situ by m-chlorobenzoic acid regio- and stereoselectively (57JA3234, 93JA7593). [Pg.285]

In the synthesis of carpamic acid (98), Mitsutaka and Ogawa have used 1,2-dihydropyridine as a starting material [80H(14)169]. Photooxygenation of dihydropyridine 8h afforded enr/o-peroxide 96. Subsequent stereoselective nucleophilic reaction of 96 with ethyl vinyl ether in the presence of tin chloride gave tetrahydropyridinol 97, which was then converted into carpamic acid (98) in six more steps. [Pg.291]

Introduction of an oxygen substituent at C-6 of a Hantzsch-type dihydropyridine having a sulfinyl group at C-5 affects the reduction of ketones with respect to both reactivity and stereoselectivity <96CC2535>. [Pg.230]

Asymmetric reduction of ketones. Pioneering work by Ohno et al. (6, 36 7, 15) has established that l-benzyl-l,4-dihydronicotinamide is a useful NADH model for reduction of carbonyl groups, but only low enantioselectivity obtains with chiral derivatives of this NADH model. In contrast, this chiral 1,4-dihydropyridine derivative (1) reduces a-keto esters in the presence of Mg(II) or Zn(II) salts in >90% ee (equation I).1 This high stereoselectivity of 1 results from the beneficial effect... [Pg.32]

Ducatti DRB, Massi A, Noseda MD, Duarte MER, Dondoni A (2009) Dihydropyridine C-glycoconjugates by organocatalytic Hantzsch cyclocondensation. Stereoselective synthesis of alpha-threofuranose C-nucleoside enantiomers. Org Biomol Chem 7 1980-1986... [Pg.271]

Cycloaddition reaction of the l-acyl-l,2-dihydropyridine derivative 240 with methyl cyanodithioformate afforded adduct 241, which was converted by three steps to solenopsin A (Id) (Scheme 13) (399). This route constitutes a completely stereoselective synthesis of this alkaloid however, details are not available. [Pg.245]

The Lewis acid-catalyzed three-component reaction of dihydropyridines, aldehydes, and />-substituted anilines efficiently yields highly substituted tetrahydroquinolines in a stereoselective manner, through a mechanism believed to be imine formation followed by formal [4-1-2] cycloaddition (Scheme 41). The 1,4-dihydropyridine starting materials were also prepared in situ by the nucleophilic addition of cyanide to pyridinium salts, creating in effect a one-pot four-component reaction <20030L717>. [Pg.733]

Reviews on stoichiometric asymmetric syntheses M. M. Midland, Reductions with Chiral Boron Reagents, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 2, Chap. 2, Academic Press, New York, 1983 E. R. Grandbois, S. I. Howard, and J. D. Morrison, Reductions with Chiral Modifications of Lithium Aluminum Hydride, in J. D. Morrison, ed.. Asymmetric Synthesis, Vol. 2, Chap. 3, Academic Press, New York, 1983 Y. Inouye, J. Oda, and N. Baba, Reductions with Chiral Dihydropyridine Reagents, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 2, Chap. 4, Academic Press, New York, 1983 T. Oishi and T. Nakata, Acc. Chem. Res., 17, 338 (1984) G. Solladie, Addition of Chiral Nucleophiles to Aldehydes and Ketones, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 2, Chap. 6, Academic Press, New York, 1983 D. A. Evans, Stereoselective Alkylation Reactions of Chiral Metal Enolates, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 3, Chap. 1, Academic Press, New York, 1984. C. H. Heathcock, The Aldol Addition Reaction, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 3, Chap. 2, Academic Press, New York, 1984 K. A. Lutomski and A. I. Meyers, Asymmetric Synthesis via Chiral Oxazolines, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 3, Chap. [Pg.249]

A reduction of symmetrically substituted dihydropyridines 358 to the corresponding hexahydro derivatives 359 can be executed at 50 °C under the action of a mild reducing agent —triethylsilane [307]. At room temperature, on the other hand, the reaction stops at the formation of tetrahydro derivatives 360 (Scheme 3.95). Both processes are stereoselective. [Pg.112]

There are several publications devoted to oxidative additions to dihydropyridines [337, 338, 339, 340, 341]. For instance, the addition of stochiometric amounts of iodine in a methanol solution of dihydropyridine 309 gives iodi-nated tetrahydropyrimidine 310 in a stereoselective manner [337]. The same result is obtained when the reaction is performed with AModosuccinimide (NIS) (Scheme 3.107). Interestingly, when the process is carried out in tetra-hydrofuran the incorporation of the succinimide moiety at position 2 yields 3-iodo-2-succinimidotetrahydropyridine 311. Using Af-bromosuccenimide, TV-chlorosuccenimide and 7V-fluoropyridinium trifluoromethanesulfonate produces 3-bromo-, 3-chloro- and 3 flouro-substituted pyridines [337]. [Pg.118]

Stereoselective vicinal diamination of dihydropyridines 309 by electrophilic interaction with iodine in the presence of secondary amines leading to tetrahydropyrimidines 312 is described in [338, 339] (Scheme 3.107). The... [Pg.118]

With an amino acid-derived chiral auxiliary employed in the chloroformate, reaction of silyl enol ethers with isoquinolinium salts showed not only regiospecificity, but some stereoselectivity as well (Equation 61) <1999SL1154>. The addition of ketene silyl acetals to an W-acylpyridinium salt containing a chiral 2,2-dimethylox-azolidine at C-3 gave 1,4-dihydropyridines with excellent stereoselectivity <2002JA8184>. [Pg.70]

The oxidation of iV-methoxycarbonyl-l,2-dihydropyridine 56 with K 2-chloroperbenzoic acid results in /ra j-dioxygenation of the 5,6-alkene to give the allylic alcohol 57<1998JOC10001> (Scheme 16). The reaction is thought to proceed via an unstable aminoepoxide which is regio- and stereoselectively trapped by m-chloiobenzoic acid. [Pg.180]

The reduction of N-(fi-indolylethyl)-pyridinium salts [e.g. (117)] by means of sodium dithionite is accompanied by cyclization in the acidic reaction medium of the 1,4-dihydropyridine so generated, with the formation of tetracyclic bases [e.g. (118)] that are useful as models for the synthesis of vallesiachotamine. If, however, the reaction medium is buffered, the intermediate 1,4-dihydropyridine can be isolated subsequent acid-induced cyclization of this gives the thermodynamically more stable tetracyclic base (119), containing an equatorial substituent at C-15 a high degree of stereoselectivity at positions 3 and 15 is therefore possible in this synthetic approach.77"... [Pg.176]

After coordination with the azine nitrogen, the activated complex 95 (Scheme 14a) undergoes a stereoselective diallylation to afford the fra s-2,6-diallyl-tetrahydro-pyridine (81). Furthermore, 81 can be transformed into its c -isomer (96) by heating. Isomerization can also occur at a dihydropyridine (DHP) intermediate following incorporation of an aUcyl group via organometallic attack upon a pyridine in a one-pot transformation (Scheme 14b) [88-90]. [Pg.139]

Coenzyme NAD(P)+ involves a nicotinamide derivative and the transfer of a hydrogen species in a stereoselective manner via a 1,4-dihydropyridine (47 Scheme 10) and has led to much work on the reduction of NAD and its simpler derivatives (46 R = PhCH2, C12H25). Most work has been done on the stereoselective reduction of ketones, but heteroaromatic cations have also been reduced (see Section 3.6.2.3). Both single-electron transfer (SET) and direct hydride transfer mechanisms have been pro-posed.2°... [Pg.584]

Stereoselective Diels-Alder reactions have been reported in several cases. Enantioselective Diels-Alder reactions of l-phenoxycarbonyl-l,2-dihydropyridine with 1-alkylated acryloyl-pyrazolidin-3-ones using a chiral cationic palla-dium-phophinooxazolidine catalyst afforded chiral isoquinuclidines with excellent enantioselectivity <2005TL5677>. Bismuth(lll) chloride-mediated diasteroselective intramolecular [4-f2] cycloaddition reactions of A-allyl derivatives of pyrazole aldehydes led to fused sulfur-containing pyrazole heterocycles <2003SC3063>. A highly diastereoselective intramolecular hetero-Diels-Alder approach toward tetracyclic pyrazoles from 5-(3-methyl-2-butenylthio)-3-methyl-l-phenyl-4-pyrazolecarboxaldehyde has been reported <1997SL1155>. [Pg.42]

The ability of coenzyme NAD(P)+ (57, R = sugar) and its mimics to accept and deliver hydride ion stereoselectively via 1,4-dihydropyridine intermediates has spurred much interest. Much work involving NADIP)" " and its simpler derivatives (56 R = PhCH2, BNAH R = C12H25, DNAH) as chiral reducing agents has been reported. ... [Pg.13]

Treatment of lV-methanesulfonyl-l,4-dihydFopyridine with n-butyllithium, followed by benzyl bromide, leads to the corresponding lV-l-(2-phenylethyl)sulfonyl-l,4-dihydropyridine in low yield. The sulfonamide shown in Scheme 131 (entry c) has proved a valuable c -isoprenoid synthon which allows the two-step C -homologation of allyl halides. This synthon was used for the remarkable two-step stereoselective synthesis of nerol from 3-methyl-2-butenyl chloride (Scheme 131, entry c). Finally, the a-chloro dicarbanion of 4-(a-chlon>methanesulfonyl)morpholine is readily availabl on reaction with 2 equiv. of n-butyllithium in THF, and it leads to the corresponding dimethyl derivative with no detectable monoalkylated product or starting sulfonamide on methylation. Intramolecular versions of these reactions allow the low yield synthesis of neopentyl cyclopropanesulfonate (scheme 131, entry d) and the efficient preparation of cyclopropanesulfomorpholine (scheme 131, entry e). ... [Pg.181]

Schleifer K-J. Stereoselective characterization of the 1,4-dihydropyridine binding site at L-type calcium channels in the resting state and the opened/inactivated state. J Med Chem 1999 42 2204-11. [Pg.388]

Stereoselective epoxidation of alkenes, desymmetrization of maso-TV-sulfonylaziri-dines, Baeyer-Villiger oxidation of cyclobutanones, Diels-Alder reactions of 1,2-dihydropyridines, and polymerization of lactides using metal complexes of chiral binaphthyl Schiff-base ligands 03CCR(242)97. [Pg.164]


See other pages where Dihydropyridines stereoselectivity is mentioned: [Pg.270]    [Pg.274]    [Pg.284]    [Pg.307]    [Pg.307]    [Pg.309]    [Pg.841]    [Pg.436]    [Pg.83]    [Pg.266]    [Pg.162]    [Pg.429]    [Pg.99]    [Pg.261]    [Pg.92]    [Pg.48]    [Pg.276]    [Pg.378]    [Pg.181]    [Pg.273]    [Pg.104]    [Pg.336]    [Pg.297]    [Pg.162]    [Pg.1071]    [Pg.122]    [Pg.779]    [Pg.429]   
See also in sourсe #XX -- [ Pg.222 ]




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1.4- Dihydropyridines

Dihydropyridine

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