First mechanosynthesis of piperlotines A,C, and derivatives through solvent-free Horner–Wadsworth–Emmons reaction

Piperlotines are natural products characterized by an α,β-unsaturated amide moiety. These compounds found wide applications in Medicinal Chemistry like antibacterials, cytotoxic agents, anticoagulants, among others. To date, diverse methods of synthesis have been reported for piperlotines, but involving the use of catalysts, hazard reagents, anhydrous media or coupling reagents. Thus, in this work, we developed a greener method of synthesis of piperlotines A, C, and derivatives, through mechanochemical activation under solvent-free conditions. The reaction of a β-amidophosphonate, K₂CO₃, and an aromatic aldehyde afforded target compounds in moderate to good yields (46–77%), in an open atmosphere by grinding. It is worth to mention that this mechanochemical process was under thermodynamic control because just E isomer was isolated for every reaction. Moreover, synthesized piperlotines have been predicted by means of chemoinformatic analysis as potential therapeutic agents for the treatment of arthritis or cancer.     

Recent topics of the natural product synthesis by Horner–Wadsworth–Emmons reaction

The Horner–Wadsworth–Emmons (HWE) reaction has become well established among existing methodologies for the highly stereoselective olefination of carbonyl compounds. The reliability of this reaction in terms of its robustness, high stereoselectivity, and broad substrate scope permit retrosynthetic disconnection of the olefin bond in α,β-unsaturated carbonyl intermediates in natural product synthesis. This review discusses recent applications of the HWE reaction in natural product synthesis, highlighting its use for carbon chain elongation, coupling reactions of synthetic segments, ring-closing reactions, tandem reactions including HWE olefination, and asymmetric reactions.     

The Wittig–Horner reaction for the synthesis of neratinib

The Wittig–Horner reaction is a classic method to get alkenes by reaction phosphonates with carbonyl compounds. In this study, it was used for the synthesis of the anticancer drug neratinib. In this method, ethyl diethoxyphosphinylacetate and dimethylaminoacetaldehyde diethylacetal, replacing (E)-4-(dimethylamino)but-2-enoyl acid hydrochloride and oxalyl chloride, were used to synthesize the 6-position side chain of neratinib.     

Task-Specific Ionic Liquid as Reagent and Reaction Medium for the One-Pot Horner–Wadsworth–Emmons–Type Reaction Under Microwave Irradiation

A task-specific imidazolium-based phosphinite ionic liquid (IL-OPPh₂) was used as the dual solvent–reagent for the synthesis of E-cinamates and coumarin derivatives via the one-pot Horner–Wadsworth–Emmons–type reaction. The ionic liquid containing its corresponding phosphinite moiety was reacted with α-chloro esters and benzaldehyde or salicylaldehyde derivatives in the presence of sodium methoxide under microwave irradiation to produce the related E-cinamates or coumarins, respectively. The satisfactory results were obtained with good yields, short reaction time, and simple experimental procedure.     

Wittig–Horner Approach for the Synthesis of Tamoxifen

A stereoselective synthesis of Z‐tamoxifen, a tetra‐substituted alkene with antiestrogenic activity, is described. The Wittig–Horner reaction has been employed as the key step to establish the olefin stereochemistry.     

Interaction of poly-L-lysine with photosynthetic reaction center for the Langmuir–Blodgett film preparation

The interaction between poly-L-lysine (PLL) and photosynthetic reaction center (RC) from Rodopseudomonas viridis was studied with special interest for the Langmuir–Blodgett (LB) film preparation. PLL of low concentration (0.5mM) in the subphase of the LB trough as a counterion stabilized the protein at the air/water interface and enhanced the protein deposition efficiency onto the substrate. PLLs of various degree of polymerization (n=1, 5, 10, 15 and 20) were synthesized and the effect of each PLL was examined. Enhancement of the deposition of RC was observed using high n peptide (n=10, 15 and 20) but not using low n one (n=1 and 5). When PLL (n=1, 5, 10, 15 and 20) was added to the RC solution, the protein–protein association and the subsequent precipitation of RC occurred. Highly polymerized PLLs were effective on both RC deposition and RC precipitation suggesting that RCs spread at air/water interface were linked by PLL. The number of PLL molecules which were adsorbed on one RC molecule was 9.0 (±1.5) and 6.6 (±0.5) in the case of n=10 and 20 of PLL, respectively.     

A facile carbothermal preparation of Sn–Co–C composite electrodes for Li-ion batteries using low-cost carbons

Sn–Co–C composites were prepared by carbothermal reaction of ball-milled precursors. X-ray diffraction and ¹¹⁹Sn Mössbauer spectroscopy of the original composites revealed the predominance of Sn and CoSn₂ phases for those samples prepared with a high Sn/Co ratio. Electron microscopy images showed a homogeneous dispersion of sub-micrometric metallic particles in the carbon matrix. Galvanostatic cycling at several kinetic rates revealed that Sn₇Co₁C₉₂ and Sn₈Co₄C₈₈ are able to maintain 400 mA h g^?1 after 40 cycles at 35 mA g^?1. The large CoSn₂ contribution revealed by Mössbauer spectroscopy in the original and cycled electrodes is responsible for the good electrochemical performance. This interpretation is also supported by impedance spectroscopy measurements.     

On the stereochemistry of the Horner—Emmons reaction between 3-functionally substituted 2-methyl-2-propenylphosphonates and aliphatic aldehydes

The reaction of diethyl 3-ethoxycarbonyl-2-methyl-2-propenylphosphonate (1) with 3-methylbutanal (2) in the system solid MOH (M=K, Na, Li)-benzene without phase transfer catalysts affords ethyl 3,7-dimethyl-2,4-octadienoate with the ratios of 2E,4E stereoisomer (3a) to 2Z,4E-stereoisomer (3b) of 4456, 4654, and 6040 for KOH, NaOH, and LiOH, respectively. The similar tendency is observed when DMSO is substituted for benzene, although the proportion of3a in this case is 65% with any MOH used. The reaction of1 with2 in the presence of a stoichiometric amount of a quaternary ammonium hydroxide QOH (Q=NMe₄, BnNMe₃, (n-Bu)₄N) in benzene gives higher3a3b ratios than those obtained with LiOH in the former reaction system. The increase in the content of 2E,4E-isomer3a is possibly due to the growth of the population of solvent-separated ion pairs or, generally, to the increase in the distance between the charge centers in the ionic intermediates on passing from KOH to LiOH and from [Me₄N]OH to [(n-Bu)₄N]OH. The position of the equilibrium betweenE- and Z-isomers of phosphonate1 under the reaction conditions (E-1Z-13565) is almost unaffected by the nature of the cation of the base.Part 5, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1089–1094, June, 1993.     

On the stereochemistry of the Horner—Emmons reaction between 3-functionally substituted 2-methyl-2-propenylphosphonates and aliphatic aldehydes

The reaction of diethyl 3-ethoxycarbonyl-2-methyl-2-propenylphosphonate (1a) with 3-methylbutanal (2) in heterogeneous MOH (solid)-benzene systems in the presence of 5–10 mol.% of benzyltriethylammonium chloride (BTEAC) gives the reaction product (3) with a higher, for M=K, or lower, for M=Li, ratio of 2E,4E and 2Z,4E-stereoisomers than that observed in the absence of BTEAC. Tetrabutylammonium bromide (TBAB) as a catalyst of the reaction1a + 2 3 in the system KOH (solid)-wet benzene leads to a higher [2E,4E-3][2Z,4E-3] ratio than BTEAC; this ratio grows from 4456 without TBAB to 8020 at 100 mol.% of TBAB. In the latter case the stereochemical outcome of the reaction is similar to that obtained when tetrabutylammonium hydroxide in dry benzene is used as the deprotonating agent. The corresponding diisopropyl phosphonate (1b) and 3,7-dimethyloctanal (4a) interact in the system KOH (solid)-wet benzene-TBAB to give hydroprene (5) containing 88 % of the 2E,4E-isomer (5a) while in the case of 1 equiv. of [(n-Bu₄)N]OH in dry benzene the content of5a is 92 %. Diisopropyl 3-isopropoxycarbonyl-2-methyl-2-propenylphosphonate (1c) and 7-methoxy-3,7-dimethyloctanal (4b) under either of these conditions afford methoprene (6) containing 93 % of the 2E,4E-isomer.Part 6, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1094–1098, June, 1993.     

A copper(II)-catalyzed,sequential Michael–aldol reaction for the preparation of 1,2-dihydroquinolines

A copper(II)-catalyzed, sequential Michael addition-aldol condensation reaction of N-carboxybenzyl-protected aminobenzaldehyde with various α,β-unsaturated N-acyl pyrroles is described. Substrate scope was found to include both aryl and aliphatic N-acyl pyrroles as the Michael acceptors, and isolated product yields as high as 93% were observed. The use of acetonitrile as the reaction solvent proved to be crucial for catalysis, both to function as a labile ligand for copper, as well as an agent to minimize hydrolytic catalyst poisoning.     

Synthesis of non-natural l-alanine derivatives using the aza-Cope–Mannich reaction

Non-natural l-alanine derived trans-octahydrocyclohepta[b]pyrroles were synthesized with high enantiomeric purity using the aza-Cope–Mannich reaction. The study showed that the conditions of the aza-Cope–Mannich reaction and metal catalysed cyclization are mild enough to be applied to the synthesis of molecules with stereocenters, which are prone to racemization. We believe that these compounds will be of interest to medicinal chemists.     

ortho-Quinodimethane from anthracene epidioxide: Scope of the Diels–Alder reaction and mild preparation of naphthalene derivatives

The thermal isomerisation of anthracene epidioxide 3 has been known to give phenylenedioxy-ortho-quinodimethane 5 as a reactive transient. We presented herein the scope of the Diels–Alder reaction of this transient 5 with some dienophiles. In addition, a mild synthesis of naphthalene derivatives has been developed via base-induced cleavage of the obtained Diels–Alder adducts.     

A new method for the preparation of fluoro-λ-sulfanenitriles: reaction of sulfimides with Selectfluor™

Several diaryl(fluoro)-λ⁶-sulfanenitriles 3 were synthesized by the reaction of S,S-diarylsulfimides 1 with Selectfluor™. This reaction also allows the first preparation of heterocyclic fluoro-λ⁶-sulfanenitrile, 5-fluoro-10,10-dioxo-5,10-dihydro-5λ⁶,10λ⁶-thianthren-5-nitrile (5) and its molecular structure was determined by X-ray crystallographic analysis.     

Baeyer–Villiger reaction of Wieland–Misher ketone derivatives: an alternative to the dienone–phenol rearrangement

This paper demonstrates the regioselectivity of the Baeyer–Villiger reaction of dicarbonylated compounds such as Wieland–Misher ketone derivatives in favour of oxygen insertion only between the quaternary carbon of the ring junction and the neighbouring carbonyl group. Further reaction sequences allow the formation of various compounds, including phenols and naphtalenones, the later being similar to the result of the dienone-phenol rearrangement of 4-acylcyclohexan-2,5-dienones already described in the literature, as well as 2-carboxy cyclohexenones which might be used as synthons for the synthesis of complex natural products. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASWieland–Misher ketone / Baeyer–Villiger / regioselectivity     

Sequential acid/base-catalyzed polycyclization of tryptamine derivatives. A rapid access to Büchi's ketone

[reaction: see text] The development of an efficient and diastereoselective methodology that allows the rapid construction of the tetracyclic core of the Aspidosperma and Strychnos alkaloid families is described. Our approach relies upon two key steps: a sequential silica gel/potassium tert-butoxide polycyclization of a tryptamine precursor and a tandem oxidative decarboxylation/ring-closing reaction. The assembly of Büchi's ketone, a key intermediate in the synthesis of vindorosine, has been accomplished using this approach.     

Application of the Mössbauer spectroscopy to the study of the oxidation state of azaferrocene derivatives

Azaferrocene has two active sites of iron and nitrogen atoms. Drastic change of the oxidation state in iodine oxidation of azaferrocene is observed by introducing the methyl substituents into the pyrrole ring, while all the N-methylates show a similar electronic state. It was revealed that an introduction of methyl substituent to the pyrrole ring promotes the oxidation of nitrogen atom in pyrrole ring more than the central iron atom.