- Intramolecular Photochemical Hydrogen Abstraction in 2-Alkylpyrazines and 2-Alkylpyridines
-
Photochemical hydrogen abstraction in 2-alkylpyrazines 5-8 and 2-alkylpyridines 9-11 proceeds analogously to the process of eq 1.Hydroxylic solvent causes quantum yields for pyrazine fragmentation products (Φp) to increase about 1 order of magnitude.Pyridine fragmentation takes place from both singlet and triplet states.Pyrazine fragmentations follow Stern-Volmer kinetics with modest bond strength selectivity (1 deg : 3 deg ca. 1:17 for 5a and 5c).Methyl substitution lowers the rate of abstraction in pyrazines and trifluoromethyl substitution increases Φp in pyridines.It is suggested that these effects reflect changes in the n?* and ??* character of the reactive excited states.
- Mukherjee, Ashis,Duggan, Sandhya A. M.,Agosta, William C.
-
-
Read Online
- Unlocking the Accessibility of Alkyl Radicals from Boronic Acids through Solvent-Assisted Organophotoredox Activation
-
Despite their prevalence in organic synthesis, the application of boronic acids (BAs) as alkyl radical precursors in visible-light-assisted photocatalyzed reactions has been limited by their high oxidation potential. This study demonstrates the prominent
- Ranjan, Prabhat,Pillitteri, Serena,Coppola, Guglielmo,Oliva, Monica,Van der Eycken, Erik V.,Sharma, Upendra K.
-
p. 10862 - 10870
(2021/09/08)
-
- Odd-Even Effect on the Spin-Crossover Temperature in Iron(II) Complex Series Involving an Alkylated or Acyloxylated Tripodal Ligand
-
In the context of magneto-structural study, a relatively short alkyl group was introduced to anionic spin-crossover (SCO) building blocks based on [Fe(py3CR)(NCS)3]-, where py3CR stands for tris(2-pyridyl)methyl derivatives. The linear alkyl and acyloxyl derivatives of Me4N[Fe(py3CR)(NCS)3] with R = CnH2n+1 (n = 1-7) and CnH2n+1CO2 (n = 1-6) were synthesized, and the magnetic study revealed that all the compounds investigated here exhibited SCO. The SCO temperature (T1/2) varied in 289-338 K for the alkylated compounds, and those of the acyloxylated ones were lower with a narrower variation width (T1/2 = 216-226 K). The crystal structures of the former with n = 3, 4, and 5 and the latter with n = 1, 4, 5, and 6 were determined, and various molecular arrangements were characterized. There is no structural evidence for a molecular fastener effect. The plots on T1/2 against n displayed a pronounced odd-even effect; the SCO temperatures of the homologues with even n are relatively higher than those of the homologues with odd n. The odd-even effect on T1/2 may be related with the entropy difference across the SCO, rather than crystal field modification or intermolecular interaction. The present work will help molecular design to fine-tune T1/2 by means of simple chemical modification like alkylation and acyloxylation.
- Ishida, Takayuki,Kashiro, Atsushi,Kohno, Wakana
-
supporting information
(2020/08/05)
-
- Enantioselective Alkylation of 2-Alkylpyridines Controlled by Organolithium Aggregation
-
Direct enantioselective α-alkylation of 2-alkylpyridines provides access to chiral pyridines via an operationally simple protocol that obviates the need for prefunctionalization or preactivation of the substrate. The alkylation is accomplished using chiral lithium amides as noncovalent stereodirecting auxiliaries. Crystallographic and solution NMR studies provide insight into the structure of well-defined chiral aggregates in which a lithium amide reagent directs asymmetric alkylation.
- Gladfelder, Joshua J.,Ghosh, Santanu,Podunavac, Ma?a,Cook, Andrew W.,Ma, Yun,Woltornist, Ryan A.,Keresztes, Ivan,Hayton, Trevor W.,Collum, David B.,Zakarian, Armen
-
supporting information
p. 15024 - 15028
(2019/10/22)
-
- The one-pot synthesis of pyridine derivatives from the corresponding 1,5-dicarbonyl compounds
-
The optimization of the one-pot, acid-promoted synthesis of pyridine and alkylpyridine derivatives from simple alkyl-1,5-dicarbonyl derivatives and via the corresponding oxime intermediate is described. Of all the combinations of and solvents tested, the use of HCl in refluxing dioxane was found to result in the highest chemical yields. Twelve pyridines were prepared using this method.
- Mihara, Hiromichi,Miyakoshi, Takeru,Kikuchi, Yui,Konno, Hiroyuki
-
p. 1375 - 1383
(2019/12/23)
-
- Manganese-Catalyzed Kumada Cross-Coupling Reactions of Aliphatic Grignard Reagents with N-Heterocyclic Chlorides
-
Herein we report the use of manganese(II) chloride for the catalytic generation of C(sp 2)-C(sp 3) bonds via Kumada cross-coupling. Rapid and selective formation of 2-alkylated N-heterocyclic complexes were observed in high yields with use of 3 mol% MnCl 2 THF 1.6 and under ambient reaction conditions (21 °C, 15 min to 20 h). Manganese-catalyzed cross-coupling is tolerant toward both electron-donating and electron-withdrawing functional groups in the 5-position of the pyridine ring, with the latter resulting in an increased reaction rate and a decrease in the amount of nucleophile required. The use of this biologically and environmentally benign metal salt as a catalyst for C-C bond formation highlights its potential as a catalyst for the late-stage functionalization of pharmaceutically active N-heterocyclic molecules (e.g., pyridine, pyrazine).
- Petel, Brittney E.,Purak, Merjema,Matson, Ellen M.
-
supporting information
p. 1700 - 1706
(2018/07/13)
-
- Cross-coupling reactions through the intramolecular activation of Alkyl(triorgano)silanes
-
(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).
- Nakao, Yoshiaki,Takeda, Masahide,Matsumoto, Takuya,Hiyama, Tamejiro
-
supporting information; scheme or table
p. 4447 - 4450
(2010/08/19)
-
- Zn-promoted regio- and sequence-selective one-pot joining reactions of three components: vinylpyridines, alkyl iodides, and carbonyl compounds (or nitriles)
-
Addition of alkyl iodides (3) into the solution containing 2-(or 4-)vinylpyridine (1 or 2) and carbonyl compounds (6) in the presence of Zn-powder (99.9%) in acetonitrile under refluxing brought about regio- and sequence-selective joining reaction of thre
- Mineyama, Kenji,Maekawa, Hirofumi,Kohsaka, Akihiro,Yamamoto, Yoshimasa,Nishiguchi, Ikuzo
-
experimental part
p. 7706 - 7711
(2009/12/04)
-
- Nickel-catalyzed cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with alkyl grignard reagents using (Z)-3,3-dimethyl-1,2- bis(diphenylphosphino)but-1-ene as ligand
-
A combination of nickel(II) acetylacetonate and (Z)-3,3-dimethyl-1,2- bis(diphenylphosphino)but-1-ene catalyzes cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with alkyl Grignard reagents. Not only primary but also secondary alkyl Grignard reagents can be employed. Georg Thieme Verlag Stuttgart.
- Kanemura, Shigenari,Kondoh, Azusa,Yorimitsu, Hideki,Oshima, Koichiro
-
scheme or table
p. 2659 - 2664
(2009/04/05)
-
- Nickel catalyzed cross-coupling of modified alkyl and alkenyl Grignard reagents with aryl- and heteroaryl nitriles: Activation of the C-CN bond
-
The nickel catalyzed cross-coupling of alkyl and alkenyl Grignard reagents with aryl nitrile derivatives affords good yields of the corresponding aryl alkanes or aryl alkenes via activation of the C-CN bond. To prevent direct addition of the nucleophile to the nitrile group, the reactivity of the Grignard reagent was modulated by reaction with either LiOt-Bu or PhSLi prior to cross-coupling. The optimum catalyst was determined to be NiCl2(PMe3)2, which is a convenient air stable commercially available complex.
- Miller, Joseph A.,Dankwardt, John W.
-
p. 1907 - 1910
(2007/10/03)
-
- Nickel catalyzed cross-coupling and amination reactions of aryl nitriles
-
Aryl nitriles have been found to participate in cross-coupling and amination reactions via nickel-catalyzed activation of the C-CN bond. With the development of these synthetically useful transformations, aryl nitriles can now be considered along with ary
- Miller, Joseph A.,Dankwardt, John W.,Penney, Jonathan M.
-
p. 1643 - 1648
(2007/10/03)
-
- N-Heteroarylphosphonates, Part II. Synthesis and reactions of 2- and 4- phosphonatoquinolines and related compounds
-
We extend our synthetic method for the efficient preparation of dialkoxyphosphoryl- and phosphonio-disubstituted pyridines to include the preparation of other phosphonato substituted N-heterocycles. The key to the success of this method lies in the employment of cationic N- (trifluoromethylsulfonyl)heteroarylium triflates that are activated towards nucleophilic attack. The P(O)(OR)2 group can be transformed into the P(S)(OR)2 functionality. We report first attempts to substitute the P(O)(OR)2 moiety with C-nucleophiles. In addition to our synthetic results, the X-ray structures of two (dimethoxyphosphoryl)trifluoromethanesulfonyldihydro-N-heteroarenes are discussed. We also give complete carbon (13C) and phosphorus (31P)-NMR spectra of a series of 2- and 4-phosphonic ester substituted heteroaryl compounds and their dihydro analogs.
- Haase, Mirko,Guì?nther, Wolfgang,Goì?rls, Helmar,Anders, Ernst
-
p. 2071 - 2081
(2007/10/03)
-
- Preparation of trans- and cis-2-allyl-6-alkyl(aryl)-1,2,3,6-tetrahydropyridines based on the reductive trans-2,6-dialkylation of pyridine. Synthesis of (+/-)-epidihydropinidine and (+/-)-dihydropinidine
-
A general method for the preparation of unsymmetrical trans-2-allyl-6-alkyl(aryl)-1,2,3,6-tetrahydropyridine 6 based on a combination of 1,2-addition of RLi to pyridine and trans-6-allylation with triallylborane in the presence of methanol was elaborated.It was shown that trans-piperidines 6 (R = Alk, Ph) isomerize into the corresponding cis-2-allyl-6-alkyl(phenyl)-3-piperidines 14 on heating with triallylborane followed by deboronation of aminoborane (16) with methanol and an alkali.The stereochemistry of compounds 6 and 14 was determined by two-dimensional NOE spectroscopy.A possible mechanism of the formation of trans-amines 6 and their transformation into cis-isomers discussed.Alkaloids (+/-)-epidihydropinidine (trans-2-methyl-6-propylpiperidine 2a, 70percent) and (+/-)-dihydropinidine (cis-2-methyl-6-propylpiperidine 1d, 71percent) were synthesized by hydrogenation of compound 6a (R = Me) and 14a (R = Me), respectively, over Raney nickel. - Keywords: allylboration; pyridine, 1,2-addition, alkyl(aryl)lithium, triallylborane; trans- and cis-2-allyl-6-alkyl(aryl)-1,2,3,6-tetrahydropyridines; trans-cis-isomerization; stereochemistry; piperidine alkaloids; (+/-)-epidihydropinidine; (+/-)-dihydropinidine.
- Bubnov, Yu. N.,Klimkina, E. V.,Ignatenko, A. V.
-
p. 451 - 458
(2007/10/03)
-
- Stoechiometrieabhaengigkeit der Reaktion von Butyllithium mit Pyridin: ein Lithiodihydropyridin mit zusaetzlich koordiniertem Pyridin
-
Keywords: Dihydropyridine; Heterocyclen; Hydridtransfer; Lithiumverbindungen; Strukturaufklaerung
- Clegg, William,Dunbar, Lorraine,Horsburgh, Lynne,Mulvey, Robert E.
-
p. 815 - 816
(2007/10/03)
-
- Preparation of trans-2-allyl-6-alkyl(aryl)-1,2,3,6-tetrahydropyridines by reductive trans-2,6-dialkylation of pyridine. Synthesis of (±)-epidihydropinidine
-
A convenient method for the preparation of the title compounds involving the sequential treatment of pyridine with RLi (R = Alk, Ar), triallylborane and methanol is developed.
- Bubnov, Yuri N.,Klimkina, Elena V.,Ignatenko, Anatoly V.,Gridnev, Ilya D.
-
p. 1317 - 1320
(2007/10/03)
-
- A Three-Step Pyridoannelation of Carbonyl Compounds
-
The elaboration of a pyridine nucleus onto an α-methylene carbonyl compound can be accomplished through a three step reaction sequence based on the regiospecific alkylation of N,N-dimethylhydrazones with bromoethyl-1,3-dioxolane.Scope and limitations of the new method are considered.
- Marchetti, Mauro
-
p. 1761 - 1765
(2007/10/02)
-
- A Novel Regiospecific Synthesis of 2-Substituted Pyridines
-
A simple method is described for the mild and efficient conversion of pyridyl-2-alkylsulfonates into 2-alkyl and 2-arylpyridines.
- Hanessian, Stephen,Kagotani, Masahiro
-
p. 409 - 411
(2007/10/02)
-
- Alkylation of Pyridine in Free Radical Chain Reactions Utilizing Alkylmercurials
-
Pyridines or N,N,N',N'-tetramethyl-p-phenylenediamine will undergo a photostimulated free radical chain reaction with alkylmercury halides or carboxylates, yielding ring alkylated substitution products.Alkene mercuration products (R1CH(Y)CH(R2)HgX with Y=HO, RO, CH3CONH; X=Cl, CH3CO2, CF3CO2) can be used without isolation for the alkylation reaction
- Russell, Glen A.,Guo, Deliang,Khanna, Rajive K.
-
p. 3423 - 3425
(2007/10/02)
-
- Enamine Rearrangement of 2-Benzylpyridinium Salts to 2-Aminobiphenyls
-
N-Methyl-2-benzylpyridinium iodide (1c) undergoes ring opening and recyclization reactions when heated with methylammonium sulphite to give 2-methylaminobiphenyl (2c), 2-hydroxybiphenyl (3) and 2-benzylpyridine (4).A similar reaction of N-methyl-2-(p-acetylbenzyl)-, N-methyl-2-(p-acetamidobenzyl)-, N-methyl-2-(p-phthalimidobenzyl)-, N-methyl-2-(p-ethylaminobenzyl)-, N-methyl-2-(p-methylethylaminobenzyl)-, and N-methyl-2-butyl-pyridinium iodides (1e, g-k) affords 2-methylamino-4-acetylbiphenyl (2e), 2-methylamino-4-aminobiphenyl (2g = 2h), 2-methylamino-4-ethylaminobiphenyl (2i), 2-methylamino-4-methylethylaminobiphenyl (2j) and N-methyl-2-propylaniline (2k) respectively in good yields.On the other hand, N-methyl-2-(carbamylmethyl)- (1a), N-methyl-2-(cyanomethyl)- (1b) and N-methyl-2-(p-nitrobenzyl)pyridinium iodides (1d) do not undergo such a rearrangement.It has been found that the unquaternized 2-benzylpyridine when heated with methylammonium sulphite undergoes recyclization to 2-methylaminobiphenyl (2k).
- Fadda, A. A.,Sagitullin, R. S.
-
p. 707 - 710
(2007/10/02)
-
- A Convenient Method for the Regioselective Synthesis of 4-Alkyl(aryl)pyridines Using Pyridinium Salts
-
RCu.BF3 reacted with 1-ethocycarbonylpyridinium chloride at the 4-position with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridine derivatives in high yields (81-94percent).The dihydropyridines were oxidized by oxygen to give 4-alkyl(aryl)pyridines (38-68percent).Grignard reagents also reacted with 1-t-butyldimethylsilylpyridinium triflate with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridines, which were easily oxidized to give 4-substituted pyridines in higher yields than above (58-70percent).
- Akiba, Kin-ya,Iseki, Yuji,Wada, Makoto
-
p. 1994 - 1999
(2007/10/02)
-
- RECYCLIZATION OF 2-BENZYLPYRIDINIUM SALTS TO 2-AMINOBIPHENYLS
-
Under the influence of aqueous solutions of alkylammonium sulfites, substituted 2-benzylpyridinium salts undergo rearrangement to 2-aminobiphenyls.The competitive processes that occur during rearrangement of the 2-benzylpyridinium salts were studied.
- Kost, A. N.,Fadda, A.,Sagitullin, R. S.,Gromov, S. P.,Petrunina, T. I.,Sharbatyan, P. A.
-
p. 970 - 976
(2007/10/02)
-
- FACILE SYNTHESIS OF 4-SUBSTITUTED PYRIDINES USING GRIGNARD REAGENTS
-
N-t-Butyldimethylsilylpyridinium triflate (2) reacted with Grignard reagents at 4-position with almost complete regioselectivity (99percent) to afford the corresponding 1,4-dihydropyridine derivatives (3), which are easily oxidized by oxygen to give 4-substituted pyridines (4: 58-70percent).
- Akiba, Kin-ya,Iseki, Yuji,Wada, Makoto
-
p. 3935 - 3936
(2007/10/02)
-
- NICKEL-PHOSPHINE COMPLEX-CATALYZED GRIGNARD COUPLING-II; GRIGNARD COUPLING OF HETEROCYCLIC COMPOUNDS
-
A general, versatile method for alkylation and arylation of haloheterocyclic compounds is reported.In the presence of a catalytic quantity of , where dppp stands for Ph2P(CH2)3PPh2, bromothiophenes, halopyridines, haloquinoline, and haloisoquinolines reacted with alkyl and aryl Grignard reagents at room temperature or at ether refluxing temperature to give the cross-coupling products.The coupling reactions has been applied to the synthesis of isoquinoline alkaloids.Reactivities of 2-thienyl and 2-pyridyl Grignard reagents have also been examined.
- Tamao, K.,Kodama, S.,Nakajima, I.,Kumada, M.,Minato, A.,Suzuki, K.
-
p. 3347 - 3354
(2007/10/02)
-
- Regioselective Addition of Grignard Reagents to 1-Acylpyridinium Salts. A Convenient Method for the Synthesis of 4-Alkyl(aryl)pyridines
-
The addition of Grignard reagents to 1-acylpyridinium salts afforded 1-acyl-2-alkyl(aryl)-1,2-dihydropyridines and 1-acyl-4-alkyl(aryl)-1,4-dihydropyridines.The regioselectivity of this reaction, 1,2- vs. 1,4-addition, was examined and found to be dependent upon the structures of the Grignard reagent and the 1-acyl group.Pyridine, 2-picoline, and 3-picoline were studied, and in most cases, significant amounts of 1,4-addition occurred.When a catalytic amount of cuprous iodide was present, nearly exclusive 1,4-addition resulted.The crude 1,4-dihydropyridines were aromatized by heating with sulfur to provide 4-substituted pyridines and picolines in good yield and high isomeric purity.
- Comins, Daniel L.,Abdullah, Abdul H.
-
p. 4315 - 4319
(2007/10/02)
-
- Pharmaceutical compositions and methods of inhibiting gastric acid secretion
-
Pharmaceutical compositions and methods of inhibiting gastric acid secretion by administering N-alkenyl and N-alkynyl thioamides.
- -
-
-