Showing papers on "Piperidine published in 2013"
TL;DR: A generally highly efficient and broadly applicable synthesis of carboxymethyl ketones from readily available carboxylic acids and terminal alkynes is developed under exceptionally mild reaction conditions.
Abstract: Steric Bulk or Conformation Control? Optimization of P,N-bidentate ligands reveals the importance of conformation control in the development of highly efficient intermolecular trapping of reactive α-oxo gold carbene intermediates. While a pendant piperidine ring offers suitable steric bulk, fixing its conformation to provide better shielding to the highly electrophilic carbene center turned out to be crucial for the excellent reaction efficiency. A generally highly efficient and broadly applicable synthesis of carboxymethyl ketones from readily available carboxylic acids and terminal alkynes is developed under exceptionally mild reaction conditions.
108 citations
98 citations
TL;DR: In this paper, the copper-diphosphine complexes were used as homogeneous catalysts with polymethylhydrosiloxane (PMHS) under 1 atm of CO2.
90 citations
TL;DR: Three-component reaction of a series of 1-acryloyl-3,5-bisbenzylidenepiperidin-4-ones with isatin and L-proline in 1:1:1 and 1:2:2 molar ratios in methanol afforded the piperidone-grafted novel mono- and bisspiro heterocyclic hybrids in good yields.
88 citations
TL;DR: A series of novel hybrid spiro heterocycles comprising pyrrolizine, spiroxindole and piperidine moieties was synthesized chemo- regio- and stereoselectively in good yields from 1,3-dipolar cycloaddition reaction of a series of 1-acryloyl-3,5-bisarylmethylidenepiperidin-4-ones with azomethine ylides generated in situ from 5-
71 citations
TL;DR: The results show that both the rate and products distribution of this reaction depend on peculiar features of ILs as reaction media and the polarity of COS.
Abstract: Herein, the reactivity and selectivity of the reaction of O,O-diethyl 4-nitrophenyl phosphate triester (Paraxon, 1) with piperidine in ionic liquids (ILs), three conventional organic solvents (COS), and water is studied by 31P NMR, UV–vis, and GC/MS. Three phosphorylated products are identified as follows: O,O-diethyl piperidinophosphate diester (2), O,O-diethyl phosphate (3), and O-ethyl 4-nitrophenyl phosphate diester (4). Compound 4 also reacts with piperidine to yield O-ethyl piperidinophosphate monoester (5). The results show that both the rate and products distribution of this reaction depend on peculiar features of ILs as reaction media and the polarity of COS.
69 citations
TL;DR: Ten new lycodine-type alkaloids, named casuarinines A-J (1-10), along with eight known analogues (11-18), were isolated from the whole plant of Lycopodiastrum casuarinoides and have an unprecedented five-membered tetrahydropyrrole ring instead of the piperidine ring.
Abstract: Ten new lycodine-type alkaloids, named casuarinines A-J (1-10), along with eight known analogues (11-18), were isolated from the whole plant of Lycopodiastrum casuarinoides . The new structures were established by spectroscopic methods and chemical transformations. Casuarinines A-D (1-4) and J (10) are common lycodine alkaloids possessing four connected six-membered rings, while tricyclic casuarinines E-H (5-8) are the piperidine ring cleavage products. In particular, casuarinine I (9) has an unprecedented five-membered tetrahydropyrrole ring instead of the piperidine ring. A plausible biosynthetic pathway to 9 is proposed. Among the compounds reported, casuarinine H (8) exhibited significant neuroprotective effect against hydrogen peroxide (H₂O₂)-induced neuronal cell damage in human neuroblastoma SH-SY5Y cells, while casuarinines C (3) and I (9) showed moderate inhibitory activity against acetylcholinesterase (AChE).
63 citations
TL;DR: In this article, Ni/Al2O3, Ni/MgAlO, and Ni/mgO catalysts were studied for the hydrogenation of pyridine to piperidine.
Abstract: Ni/Al2O3, Ni/MgAlO, and Ni/MgO catalysts were studied for the hydrogenation of pyridine to piperidine. Microcalorimetric adsorption and infrared spectroscopy were used to study the adsorption of CO...
63 citations
TL;DR: Unprotected secondary amines are directly alkylated by C-H functionalization adjacent to nitrogen, thereby opening new routes toward the synthesis of α- and β-alkylated N-heterocycles.
59 citations
TL;DR: A systematic study on the substrate and reagent scope of this remarkable transformation featuring an unprecedented direct transmetalation on a Ru(II)-H species and the successful use of a variety of heteroarylboronic esters as coupling partners proved the power of this direct functionalization method.
Abstract: Transition-metal-catalyzed sp3 CH activation has emerged as a powerful approach to functionalize saturated cyclic amines. Our group recently disclosed a direct catalytic arylation reaction of piperidines at the α position to the nitrogen atom. 1-(Pyridin-2-yl)piperidine could be smoothly α-arylated if treated with an arylboronic ester in the presence of a catalytic amount of [Ru3(CO)12] and one equivalent of 3-ethyl-3-pentanol. A systematic study on the substrate and reagent scope of this transformation is disclosed in this paper. The effect of substitution on both the piperidine ring and the arylboronic ester has been investigated. Smaller (pyrrolidine) and larger (azepane) saturated ring systems, as well as benzoannulated derivatives, were found to be compatible substrates with the α-arylation protocol. The successful use of a variety of heteroarylboronic esters as coupling partners further proved the power of this direct functionalization method. Mechanistic studies have allowed for a better understanding of the catalytic cycle of this remarkable transformation featuring an unprecedented direct transmetalation on a RuIIH species.
47 citations
TL;DR: The catalytic asymmetric aminoallylation of chiral aldehydes is developed as a new method for the catalyst controlled synthesis of syn- and anti-1,3-aminoalcohols and highlighted in the synthesis of the sedum alkaloids (+)-sedridine and (+)-allosedridine both of which have their final carbon incorporated during closure of the piperidine ring via a hydroformylation with formaldehyde.
TL;DR: Reductive alkylations of substituted lactams demonstrated good to excellent 1,3-asymmetric induction to provide the corresponding di- or trisubstituted pyrrolidine/piperidine in 6:1, 11:1 (Et3SiH), and 20: 1 (catalytic hydrogenation) cis/trans diastereoselectivity, respectively.
Abstract: Full details of the direct and general method for the reductive alkylation of tertiary lactams and amides to give tertiary sec-alkylamines are presented. This one-pot method consists of in situ activation of a lactam or an amide with Tf2O/DTBMP, addition of a Grignard reagent, and reduction of the resulting iminium intermediates. Alkyl, benzyl, and aryl Grignard reagents and several reductants or reducing conditions (LiAlH4, NaBH4, Hantzsch ester, Bu3SnH, Pd(OH)2/C, H2) could be used effectively. Reductive alkylations of substituted lactams demonstrated good to excellent 1,3-asymmetric induction to provide the corresponding di- or trisubstituted pyrrolidine/piperidine in 6:1 (LiAlH4), 11:1 (Et3SiH), and 20:1 (catalytic hydrogenation) cis/trans diastereoselectivity, respectively. The versatility of this methodology was demonstrated by its application in the concise stereoselective synthesis of piperidine alkaloid (−)-morusimic acid.
TL;DR: A general methodology for the stereoselective synthesis of 2-(2-hydroxyalkyl)piperidine alkaloids by ring-rearrangement metathesis of nitroso Diels-Alder cycloadducts is reported.
Abstract: A general methodology for the stereoselective synthesis of 2-(2-hydroxyalkyl)piperidine alkaloids by ring-rearrangement metathesis of nitroso Diels–Alder cycloadducts is reported. The approach is illustrated by the formal synthesis of porantheridine and the total synthesis of andrachcinidine through a diastereodivergent allylation of an N-alkoxy bicyclic lactam. The asymmetric synthesis of the latter alkaloid provides new insights into the configurational stability of cycloadducts between chloronitroso reagents and cyclopentadiene.
TL;DR: In this article, a series of 1-aryl-5-trifluoromethyl triazoles were synthesized in high yield by a one-pot three-component reaction of arylboronic acids, sodium azide, and active methylene ketones.
TL;DR: The monomeric aluminium hydrazide H10 C5 N N(AltBu2 )Ad (4; Ad=adamantyl, NC5 H10 =piperidinyl) was obtained in high yield by hydroalumination of the corresponding hydrazone derivative 1 by the reaction with an imidoyl chloride.
Abstract: The monomeric aluminium hydrazide H10C5NNAtBu2)� Ad (4; Ad = adamantyl, NC5H10 = piperidinyl) was obtained in high yield by hydroalu- mination of the corresponding hydra- zone derivative 1. Compound 4 has a strained AlN2 heterocycle formed by a donor-acceptor bond between the b-ni- trogen atom of the hydrazide group and the aluminium atom. Opening of this bond resulted in the formation of an active Lewis pair that was able to cooperatively activate carbon dioxide or isocyanates. Insertion of the hetero- cumulenes into the AlN bond selec- tively afforded a carbamate and two urea derivatives in high yield. In the first step, phenyl isocyanate gave the adduct 6, which has the oxygen atom coordinated to the aluminium atom and its central carbon atom bound to the nitrogen atom of the piperidine moiety. Adduct 6 represents a reason- A intermediate state for these activa- tion processes. The applicability of hy- droaluminated compounds, such as 4, in organic synthesis was demonstrated by the reaction with an imidoyl chlor- ide, which gave the corresponding ami- drazone derivative 9.
TL;DR: In this article, an efficient and one-pot quantitative procedure for the preparation of functionalized piperidine derivatives from pseudo five-component reactions of aromatic aldehydes, substituted anilines, and ethyl/methyl acetoacetate (molar ratio: 2/2/1) in the presence of acidic ionic liquids such as 1-methylimidazolium hydrogen sulfate ([Hmim]HSO 4 ), 1,1,3,3-tetramethylguanidinium perchlorate ([TMG]Cl
TL;DR: In this article, a simple and efficient method was developed for one-pot, five-component synthesis of highly functionalized piperidines from reactions of β-keto esters, aromatic aldehydes, and various amines catalyzed in acetic acid medium.
TL;DR: A density functional theoretical study showed that a suitable special orientation of piperidine rings in the structure directing agents is responsible for the formation of hierarchical Beta zeolite in this paper.
Abstract: Hierarchical Beta zeolite was prepared using piperidine based structure directing agents having at least two ammonium groups in their structure. Materials exhibited very high surface area (≈1050 m2 g−1), pore volume (2.7 mL g−1), and catalytic activity hitherto reported in the literature. A density functional theoretical study shows that a suitable special orientation of piperidine rings in the structure directing agents is responsible for the formation of hierarchical Beta.
TL;DR: In this paper, the formation of piperidine derivatives was assumed to proceed via reaction of the aldehyde with a β-ketoester-derived enolate anion to form an α-substituted β-ketoester intermediate.
TL;DR: The synthetic routes described here enabled the design of novel arginase inhibitors with improved potency and markedly different physico-chemical properties compared to ABH.
TL;DR: The molecular mechanism at the nicotinic pharmacophore and biological activities of a group of piperidine and quinolizidine alkaloid teratogens that impart a series of flexure-type skeletal defects and cleft palate in animals are reviewed.
Abstract: The exposure of a developing embryo or fetus to alkaloids from plants, plant products, or plant extracts has the potential to cause developmental defects in humans and animals. These defects may have multiple causes, but those induced by piperidine and quinolizidine alkaloids arise from the inhibition of fetal movement and are generally referred to as multiple congenital contracture-type deformities. These skeletal deformities include arthrogyrposis, kyposis, lordosis, scoliosis, and torticollis, associated secondary defects, and cleft palate. Structure-function studies have shown that plant alkaloids with a piperidine ring and a minimum of a three-carbon side-chain α to the piperidine nitrogen are teratogenic. Further studies determined that an unsaturation in the piperidine ring, as occurs in gamma coniceine, or anabaseine, enhances the toxic and teratogenic activity, whereas the N-methyl derivatives are less potent. Enantiomers of the piperidine teratogens, coniine, ammodendrine, and anabasine, also exhibit differences in biological activity, as shown in cell culture studies, suggesting variability in the activity due to the optical rotation at the chiral center of these stereoisomers. In this article, we review the molecular mechanism at the nicotinic pharmacophore and biological activities, as it is currently understood, of a group of piperidine and quinolizidine alkaloid teratogens that impart a series of flexure-type skeletal defects and cleft palate in animals.
TL;DR: Mesoporous MCM-22 zeolite (meso-MCM-21) has been prepared by treating MCM22 with sodium hydroxide solution through an organic amine-assisted reversible structural change.
Abstract: Mesoporous MCM-22 zeolite (meso-MCM-22) has been prepared by treating MCM-22 with sodium hydroxide solution through an organic amine-assisted reversible structural change. The alkaline treatment conditions, such as temperature, time, organic amine type, and its amount, were examined in detail. The desilication with sole NaOH caused an easy collapse of the crystalline structure of MWW topology. In contrast, the NaOH treatment with the coexistence of piperidine introduced mesopores of ∼20 nm into the MCM-22 crystals. Meanwhile, the calcined MCM-22 with three-dimensional (3D) MWW crystalline structure was converted to a 2D layered precursor with a well retained framework. The acid sites related to framework aluminum cations were almost intact after mesopore creation, as evidenced by pyridine or ammonia adsorption–desorption and 27Al NMR investigation. In comparison with MCM-22, meso-MCM-22 possessed a larger external surface, which mitigated effectively the steric restrictions to bulky molecules imposed by t...
TL;DR: In this paper, the authors describe the synergistic protocol developed by combinatorial Henry and Nef reaction for the synthesis of 2-substituted pyrrolidine and piperidine alkaloids containing 1,3-aminoketone and 1, 3-amino alcohol units.
TL;DR: In this paper, the properties of fully morpholine substituted sas 5c and sbs 6c phosphazenes were verified by X-ray diffraction analysis and the relationships between exocyclic OPN bond angles (alpha') and delta P-OPN shifts, and the correlation of Delta(P-N) values and Delta(delta P) or delta P -OPN shift were presented.
TL;DR: This strategy has been successfully employed in the formal synthesis of biologically active 3,4-disubstituted piperidine derivatives, (-)-paroxetine and Ro 67-8867 and a natural product, (+)-eldanolide.
Abstract: The HKR of racemic anti- or syn-3-substituted epoxy esters catalyzed by a Co(III)salen complex provides ready access to the corresponding enantioenriched 3,4-disubstituted γ-butyrolactones and 3-substituted epoxy esters. This strategy has been successfully employed in the formal synthesis of biologically active 3,4-disubstituted piperidine derivatives, (−)-paroxetine and Ro 67-8867 and a natural product, (+)-eldanolide.
TL;DR: In this article, a Friedel-Crafts-type alkylation reaction was studied between various pyrroles and α-polyfluoroalkylated cyclic imines that were activated by Lewis acids.
TL;DR: An efficient and consecutive one-pot, two-step, four-component reaction for the synthesis of trifluoromethylated spirocyclic[indole-3,4-pyrano[2,3-c]pyrazole] derivatives by the reaction of isatin, malononitrile, ethyl cyanoacetate, or Cyanoacetamide was described in this article.
TL;DR: A new method for one-pot synthesis of 2,3-substituted piperidine from N-PMP aldimine and aqueous glutaraldehyde via formal [4+2] cycloaddition is reported, involving organocatalytic direct Mannich reaction-reductive cyclization with high yields and excellent enantioselectivities.
TL;DR: In this article, the Pd-S and Pd−Se bond lengths are in the ranges 2.2795(14) and 2.3541(6)−2.3632(15) A, respectively.
01 Jan 2013