- Borane-Catalyzed Reduction of Pyridines via a Hydroboration/Hydrogenation Cascade
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We have developed a method for a B(C6F5)3-catalyzed hydroboration/hydrogenation cascade reduction of pyridines. The method was particularly effective for 2,3-disubstituted pyridines, which generated piperidines in high yields with high cis selectivity. Mechanistic studies indicated that the pyridine substrates and the piperidine products sequentially acted as bases in cooperation with B(C6F5)3to split H2. The broad functional group tolerance of the method allowed its use for the synthesis of some biologically active molecules.
- Yang, Zhao-Ying,Luo, Heng,Zhang, Ming,Wang, Xiao-Chen
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p. 10824 - 10829
(2021/09/08)
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- Regioselectivity Influences in Platinum-Catalyzed Intramolecular Alkyne O-H and N-H Additions
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The steric and electronic drivers of regioselectivity in platinum-catalyzed intramolecular hydroalkoxylation are elucidated. A branch point is found that divides the process between 5-exo and 6-endo selective processes, and enol ethers can be accessed in good yields for both oxygen heterocycles. The main influence arises from an electronic effect, where the alkyne substituent induces a polarization of the alkyne that leads to preferential heteroatom attack at the more electron-deficient carbon. The electronic effects are studied in other contexts, including hydroacyloxylation and hydroamination, and similar trends in directionality are predominant although not uniformly observed.
- Costello, Jeff P.,Ferreira, Eric M.
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supporting information
p. 9934 - 9939
(2019/12/24)
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- Regiocontrolled synthesis of (hetero)aryl and alkenyl dehydropyrrolidines, dehydropiperidines and azepenes by Ru-catalyzed, heteroatom-directed α-C-H activation/cross-coupling of cyclic enamides with boronic acids
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The synthesis of α-aryl and alkenyl pyrrolidine-, piperidine-, and azepane derivatives, through the intermediacy of cyclic enamides is described. The desired outcome is achieved through ruthenium-catalyzed, site-selective sp2 C-H activation/cro
- Beng, Timothy K.,Langevin, Spencer,Braunstein, Hannah,Khim, Monique
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supporting information
p. 830 - 834
(2016/01/15)
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- Highly enantioselective organocatalytic oxidative kinetic resolution of secondary alcohols using chiral alkoxyamines as precatalysts: Catalyst structure, active species, and substrate scope
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The development and characterization of enantioselective organocatalytic oxidative kinetic resolution (OKR) of racemic secondary alcohols using chiral alkoxyamines as precatalysts are described. A number of chiral alkoxyamines have been synthesized, and their structure-enantioselectivity correlation study in OKR has led us to identify a promising precatalyst, namely, 7-benzyl-3-n-butyl-4-oxa-5-azahomoadamantane, which affords various chiral aliphatic secondary alcohols (ee up to >99%, krel up to 296). In a mechanistic study, chlorine-containing oxoammonium species were identified as the active species generated in situ from the alkoxyamine precatalyst, and it was revealed that the chlorine atom is crucial for high reactivity and enantioselectivity. The present OKR is the first successful example applicable to various unactivated aliphatic secondary alcohols, including heterocyclic alcohols with high enantioselectivity, the synthetic application of which is demonstrated by the synthesis of a bioactive compound.
- Murakami, Keiichi,Sasano, Yusuke,Tomizawa, Masaki,Shibuya, Masatoshi,Kwon, Eunsang,Iwabuchi, Yoshiharu
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p. 17591 - 17600
(2015/02/19)
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- A short, chemo-enzymatic synthesis of both enantiomers of trans-3-hydroxypipecolic acid
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A short synthesis of both enantiomers of trans-3-hydroxypipecolic acid was based on the Suzuki-Miyaura reaction of a lactam-derived enol phosphate and the lipase-catalyzed kinetic resolution of the alcohol obtained by hydroboration/oxidation of the coupling product. The RuCl3-catalyzed oxidation of the heteroaryl group introduced by the Suzuki-Miyaura coupling eventually afforded, in six or seven steps, the target compounds in 15-17% overall yield.
- Begliomini, Stefano,Sernissi, Lorenzo,Scarpi, Dina,Occhiato, Ernesto G.
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p. 5448 - 5455,8
(2014/10/16)
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- A short, chemo-enzymatic synthesis of both enantiomers of trans-3-hydroxypipecolic acid
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A short synthesis of both enantiomers of trans-3-hydroxypipecolic acid was based on the Suzuki-Miyaura reaction of a lactam-derived enol phosphate and the lipase-catalyzed kinetic resolution of the alcohol obtained by hydroboration/oxidation of the coupling product. The RuCl3-catalyzed oxidation of the heteroaryl group introduced by the Suzuki-Miyaura coupling eventually afforded, in six or seven steps, the target compounds in 15-17% overall yield.
- Begliomini, Stefano,Sernissi, Lorenzo,Scarpi, Dina,Occhiato, Ernesto G.
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p. 5448 - 5455
(2015/11/09)
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- Alternative strategies for the stereoselective synthesis of enantioenriched 6-arylated piperidin-2-ones
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Two alternative synthetic approaches to a variety of enantioenriched 6-arylated piperidin-2-ones have been developed. The first one is based on the hydrogenation of suitably arylated chiral cyclic enehydrazides. The second approach relies on the asymmetric catalytic hydrogenation of the corresponding N-alkylated precursors. 2012 Elsevier Ltd.
- Sallio, Romain,Lebrun, Stephane,Agbossou-Niedercorn, Francine,Michon, Christophe,Deniau, Eric
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experimental part
p. 998 - 1004
(2012/09/22)
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- SN2 reaction of 2-substituted 3-piperidinol mesylate with retention of configuration: application to the asymmetric synthesis of (2R,3S)-CP-99,994
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Starting from protected (S)-3-hydroxyglutarimide 2a, the asymmetric synthesis of (2R,3S)-CP-99,994 8 was achieved. The crucial steps were a neighboring group participation leading to pyrrolidino-aziridinium intermediate 25 and the subsequent regioselectiv
- Liu, Liang-Xian,Huang, Pei-Qiang
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p. 3265 - 3272
(2007/10/03)
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- Preparation and Suzuki-Miyaura coupling reactions of tetrahydropyridine-2- boronic acid pinacol esters
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A study on the conversion of lactam-derived vinyl triflates and phosphates into the corresponding vinyl boronates was carried out. While δ-valerolactam-derived vinyl triflates were successfully converted into 1,4,5,6-tetrahydropyridine-2-boronic acid pinacol ester derivatives by Pd-catalyzed coupling reaction with both bis(pinacolato)diboron and pinacolborane, pyrrolidinone and ε-caprolactam derivatives either did not react or were readily reduced. The δ-valerolactam-derived vinyl boronates are thermally stable compounds that efficiently coupled, under Pd catalysis, with structurally diverse aryl and heteroaryl bromides and triflates, vinyl iodides and bromides, and aromatic acid chlorides, to give the corresponding 2-substituted piperidines in good to excellent yields. The number of electrophiles that can virtually be coupled with these new boronic esters makes them very useful reagents for the synthesis of N-heterocyclic compounds.
- Occhiato, Ernesto G.,Lo Galbo, Fabrizio,Guarna, Antonio
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p. 7324 - 7330
(2007/10/03)
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- Suzuki reaction of vinyl triflates from six- and seven-membered N-alkoxycarbonyl lactams with boronic acids and esters
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The Pd(0)-catalyzed reaction of vinyl triflates from N-alkoxycarbonyl lactams with different boron compounds has been studied. The coupling reaction of alkenylboronates and arylboronic acids with six- and seven-membered lactam-derived N-alkoxycarbonyl vin
- Occhiato,Trabocchi,Guarna
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p. 2459 - 2465
(2007/10/03)
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- Pd(0)-catalyzed cross-coupling reactions of boron derivatives with a lactam-derived N-Boc enol triflate
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(equation presented) The cross-coupling reaction of 2-(1-alkenyl)-1,3,2-benzodioxaboroles, obtained from alkynes and catecholborane, and other boron derivatives with a lactam-derived N-Boc enol triflate occurred under very mild conditions in a THF-water m
- Occhiato, Ernesto G.,Trabocchi, Andrea,Guarna, Antonio
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p. 1241 - 1242
(2007/10/03)
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