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Tin(II) chloride, which is insensitive to water and air, mediated the coupling reaction between alkynes and aldehydes as a Lewis acid in nitromethane to produce ( E)-α,β-unsaturated ketones by a skeletal transformation in which one alkynic carbon atom changed into an oxo carbon atom accompanied by the cleavage of a C=O bond in the starting aldehydes. This coupling reaction was promoted by a catalytic amount of a primary or secondary alkanol. The coupling reaction between 1-deuterio-2-phenylethyne and benzaldehyde with BuOH afforded 1,3-diphenyl-2-deuterio-2-propenone (2-deuteriation: 94 % D), whereas the coupling reaction between phenylethyne and benzaldehyde with BuOD afforded 1,3-diphenyl-2-propenone (2-deuteriation: 0 % D). Because almost no exchange between hydrogen and deuterium at the 2-position of 1,3-diphenyl-2-propenone occurs in either of the reactions, the coupling reaction between alkynes and aldehydes with tin(II) chloride is presumed to proceed by nucleophilic addition of alkynes to aldehydes. The cleavage of the C-O single bond generated by the nucleophilic addition might be induced by the strong oxophilicity of tin. [ABSTRACT FROM AUTHOR]

A weak Lewis acid, tin(II) chloride, which is insensitive to water and air, functioned as a catalyst for the propargylic substitution of secondary propargylic alcohols with carbon nucleophiles, such as electron-rich arenes, heteroarenes, and 1,3-dicarbonyl compounds, and nitrogen nucleophiles, such as sulfonamides, carbamates, and carboxamides, at 40-80 °C in CH3NO2 under air and exhibited a higher catalytic activity than tin(II) bromide or iodide in the propargylic substitution of 1-phenyl-2-propyn-1-ol with anisole at 40 °C in CH3NO2. The solubility of tin(II) fluoride in CH3NO2 would have to be extremely low to cause no propargylic substitution. 1-Phenyl-substituted propargylic alcohols readily reacted with all these nucleophiles, whereas 1-(4-cyanophenyl)-2-propyn-1-ol and 1-(pentafluorophenyl)-2-propyn-1-ol did not react at all with 1,2,3-trimethoxybenzene even in CH3NO2 at reflux. The 1-alkyl-substituted secondary propargylic alcohol, 1,5-diphenyl-1-pentyn-3-ol, underwent SnCl2-catalyzed propargylic substitution with electron-rich arenes and amides, although the reaction was slow even at 80 °C in CH3NO2. Thus, the SnCl2-catalyzed propargylic substitution reaction is dependent upon the stability of the propargylic carbenium ion formed upon elimination of hydroxide from the corresponding propargylic alcohol. [ABSTRACT FROM AUTHOR]

Abstract: Palladium(II)-exchanged hydroxyapatite (PdHAP; Pd/Ca ratio=ca. 1/200) was prepared by ion-exchanging with Ca2+ from calcined hydroxyapatite (2.0mmol) and Pd(NO3)2 (0.10mmol) in water (150mL) at 70°C for 24h. The PdHAP (1mol% Pd to aryl bromides) functioned as a catalyst for the Suzuki–Miyaura-type cross-coupling reaction of aryl bromides and potassium aryltrifluoroborates with triphenylphosphine (1mol%) and excess potassium carbonate at 50°C in methanol under air. This cross-coupling reaction was found to proceed in water, while the rate was slow compared with that in methanol. The heterogeneous PdHAP catalyst was used ten times repeatedly at 50°C in methanol under air, though its catalytic activity gradually declined. XRD and XRF analyses and TEM images revealed that most of palladium species would still be supported as isolated ions on the repeatedly used PdHAP, in spite of the changes of the structure and composition of PdHAP surface at the late stages in the repetitive uses and the partial leaching of Pd species at the initial stages in the repetitive uses. The gradual decline of the catalytic activity might be dependent on either the changes of PdHAP surface at the late stages or the partial leaching of Pd species at the initial stages. Still, heterogeneous PdHAP served as a reusable catalyst for Suzuki–Miyaura-type cross-coupling reaction with potassium aryltrifluoroborates. [Copyright &y& Elsevier]

Abstract: Palladium(II)-exchanged hydroxyapatite (PdHAP; for example, PdHAP-B has a Pd/Ca ratio=ca 1/200) was prepared by ion-exchanging with Ca2+ from calcined hydroxyapatite and Pd(NO3)2 in water at 70°C for 24h. The ion-exchange was revealed by inductively coupled plasma analysis; Pd2+ was almost absent in any filtrate that included over 1.6 equimolar amounts of Ca2+ relative to the amount of Pd2+ consumed. The PdHAP (1mol% Pd) functioned as a catalyst for the allylic alkylation of allyl methyl carbonate with active methylene compounds such as diethyl malonate, 2-ethoxycarbonylcyclopentanone, 2-ethoxycarbonylcyclohexanone, and 2,2-dimethyl-1,3-dioxane-4,6-dione at 50°C in water under air. Over 97% of the PdHAP was recovered by centrifugation followed by decantation, and the material could be reused. The catalytic activity of PdHAP accompanied by satisfactory yields of monoallylated products was maintained in ten repetitive uses for the allylic alkylation of allyl methyl carbonate with diethyl malonate at 50°C for 24h in water under air. From the standpoints of yield and handling, using water as a solvent was superior to using an organic medium such as ethanol, THF or DMF. Thus, this heterogeneous PdHAP-catalyzed allylic alkylation will be one of the environmentally-benign organic syntheses. [ABSTRACT FROM AUTHOR]

Abstract: Copper(II)-exchanged hydroxyapatite, prepared by ion-exchanging of Ca(II) in calcium hydroxyapatite [Ca10(PO4)6(OH)2] with Cu(NO3)2 at 70°C in water, functions as a reusable heterogeneous catalyst with neither reducing agents nor bases for azide–alkyne [3+2] cycloaddition at 50°C in water under air. [Copyright &y& Elsevier]

Abstract: 3-Alkoxypropenes, namely allyl ethers such as allyl butyl ether, allyl 2-hydroxypropyl ether, and diallyl ether, serve as reagents for the allylation of aldehydes with tin(II) chloride in the presence of a catalytic amount of [IrCl(cod)]2 in THF and H2O at 50°C to produce the corresponding homoallylic alcohols. [Copyright &y& Elsevier]

Abstract: Carbonyl allylations by allylic chlorides either with tin(IV) iodide and tetrabutylammonium iodide (TBAI) in dichloromethane or with tin(IV) iodide and sodium iodide in 1,3-dimethylimidazolidin-2-one at room temperature produced the corresponding homoallylic alcohols. The carbonyl allylations probably proceeded via the reduction of tin(IV) iodide to triiodostannate(II) species with iodide sources such as TBAI and NaI, which led to the construction of a tin(IV)-catalytic cycle based on regeneration of tin(IV) iodide via the transmetalation of homoallyloxytriiodotin to homoallyloxytrimethylsilane with iodotrimethylsilane. [Copyright &y& Elsevier]

2-Propenyl tin species, prepared from 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammonium iodide in dichloromethane, causes nucleophilic addition to aldehydes to produce the corresponding homoallylic alcohols. [Copyright &y& Elsevier]

Tin dichloride mediates the coupling reaction between alkynes and aldehydes as a Lewis acid in nitromethane to stereoselectively produce (E)-α,β-unsaturated ketones by a skeletal transformation in which one alkynic carbon atom changes into an oxo carbon atom accompanied by the cleavage of a C=O bond in the starting aldehydes. [ABSTRACT FROM AUTHOR]

The article presents diagrammatic representation of the propargylic substitution reaction of propargylic alcohols with carbon and nitrogen nucleophiles.

Foeniculoxin is a major phytotoxin produced by Italian strains of Phomopsis foeniculi. The first total synthesis is described utilizing the ene reaction and Sonogashira cross‐coupling reaction as key steps. The absolute configuration of the C6' was determined using chiral separation and an advanced Mosher's method. The phytotoxicity of the synthesized compound was demonstrated via syringe‐based infiltration into Chenopodium album and Arabidopsis thaliana leaves. Synthetic foeniculoxin induced various defects in A. thaliana leaf cells before lesion formation, including protein leakage into the cytoplasm from both chloroplasts and mitochondria and mitochondrial rounding and swelling. Furthermore, foeniculoxin and the antibiotic hygromycin B caused similar agglomeration of mitochondria around chloroplasts, highlighting this event as a common component in the early stages of plant cell death. [ABSTRACT FROM AUTHOR]

Abstract: Seven-membered metallacyclic allene compounds, 1-zirconacyclohepta-2,3,6-trienes, were synthesized by intermolecular coupling between alkynes and 1-en-3-ynes on a zirconium atom. X-ray diffraction studies and NMR spectroscopic observation indicated their seven-membered structures, although the contribution from 2-alkynyl-1-zirconacyclopent-4-ene might be considered. Benzyne, an unstable alkyne, also coupled with 1-en-3-ynes on zirconium and titanium. [Copyright &y& Elsevier]

Abstract Five-membered metallacycloallene compounds that are 2,5-disubstituted 1-zirconacyclopenta-2,3-dienes were prepared from (E)-1,4-bis(trialkylsilyl)but-1-en-3-ynes in good yields. The structures of these compounds were determined by X-ray diffraction study. Contrary to our previous study on 2,4-disubstituted 1-zirconacyclopenta-2,3-dienes, which gave alkynyl alcohols by the reaction with ketones after hydrolysis, the 2,5-bis(trialkylsilyl) complexes reacted with ketones to afford allenyl alcohols. Reactions with a nitrile gave a pyrolle compound probably via the formation of seven-membered 1-aza-2-zirconacyclohepta-3,4,7-triene ring structures. When the (E)-1,4-bis(trialkylsilyl)but-1-en-3-ynes were treated with titanium isopropoxide/ n -butyllithium followed by reaction with nitriles, the corresponding alkynyl ketones were obtained. Graphical abstract The 2,5-bis(trialkylsilyl)-1-zirconacyclopenta-2,3-diene complexes 3 , stable five-membered zirconacycloallenes, were prepared from 1,4-disilylbut-1-en-3-ynes. Complexes 3 reacted with ketones or nitrile to afford allenyl alcohols and the corresponding pyrolle, respectively. Image 1 Highlights • (E)-1,4-Bis(trialkylsilyl)but-1-en-3-ynes reacted with zirconocene and titanocene to form stable five-membered metallacycloallenes. • The synthesized 2,5-disilyl-1-zirconacyclopenta-2,3-diene complexes reacted with ketones to give allenyl alcohols after hydrolysis. • The 2,5-disilyl-1-zirconacyclopenta-2,3-diene complexes reacted with benzonitrile to give pyrolle compounds after hydrolysis. • Titanium(IV) isopropoxide was employed for the reaction with (E)-1,4-disilylbut-1-en-3-ynes and nitriles to afford alkynyl ketones. [ABSTRACT FROM AUTHOR]

A multidentate O,N,O P ligand 4 designed for early–late heterobimetallic (ELHB) complexes was synthesized. The ligand 4  has an O,N,O-tridentate ligand moiety and a triarylphosphine group. The O,N,O-moiety based on lutidine scaffold selectively coordinated to early transition metals such as titanium and niobium in the reaction with the corresponding metal alkoxides to form mononuclear complexes. Coordination of the triarylphosphine moiety to the niobium atom was negligible in the Nb-ONO P complex according to 31 P NMR spectroscopy, whereas a part of the phosphorus atom coordinated to the titanium atom in the Ti-ONO P complex. Addition of [PdCl(π-allyl)] 2 or [RhCl(cod)] 2 to the Nb-ONO P complex gave rise to the formation of ELHB complexes. Thus, the one-pot preparation of ELHB complexes was achieved by simple procedure. [ABSTRACT FROM AUTHOR]

The reactivity of the bidentate ancillary ligand 1,2-bis(dimethylphosphino)ethane (dmpe), Me 2 PCH 2 CH 2 PMe 2 , involving low-valent zirconium complexes was studied. Negishi reagent, Cp 2 Zr( n -Bu) 2 , gave zirconocene but-1-ene complexes of monocoordinated dmpe, while dicoordinated Cp 2 Zr(κ 2 -dmpe) was not formed. Cp 2 ZrEt 2 reacted with dmpe to afford Cp 2 Zr(η 2 -ethene)(κ 1 -dmpe) ( 2 ) and [Cp 2 Zr(η 2 -ethene)] 2 (μ,κ 1 -dmpe) ( 3 ). Cp 2 Zr(κ 2 -dmpe) ( 1 ) prepared by reduction of Cp 2 ZrCl 2 with Li in the presence of dmpe reacted with alkynylimine and alkynylthioamide to give the corresponding 1-aza-2-zirconacyclopenta-3,4-diene ( 6 ) and 1-thia-2-zirconacyclopenta-3,4-diene ( 8 ), respectively, whereas neither conjugated 1-en-3-ynes nor alkynes gave zirconacycle products. Reactions of 1 with iodomethane brought about oxidative addition of C-I to afford Cp 2 Zr(Me)X (X = Cl, I) species. [ABSTRACT FROM AUTHOR]

A Ph3PAuCl-SnCl2 composite, prepared in situ from Ph3PAuCl and SnCl2, catalyzed the formation of 1-benzopyrans from phenols and phenylacetylene. The Ph3PAuCl-SnCl2 composite catalyzed reaction was presumed to proceed through the successive ortho-alkenylation and O-alkenylation of phenols with phenylacetylene followed by cyclization of the prepared ortho- and O-dialkenylated phenol derivatives. Conveniently, all reactions with Ph3PAuCl-SnCl2 composite were established without rigorous exclusion of air and water. [ABSTRACT FROM AUTHOR]

Heterobimetallic complexes containing titanium and palladium were prepared from O,N,O-N,N multidentate ligands. The ligands each contained an O,N,O-tridentate part based on a 2,6-lutidine scaffold and an N,N-bidentate di(pyridin-2-yl) part. The O,N,O-moiety selectively coordinated to a titanium atom on treatment with titanium( tetraisopropoxide), although one of the di(pyridin-2-yl) groups in the N,N-moiety coordinated to the titanium atom. The N,N-bidentate di(pyridin-2-yl) moiety coordinated to the palladium atom on treatment with bis(benzonitrile) palladium(II) chloride to afford a heterobimetallic complex. The dynamic behavior of the complexes in solution was studied by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Heterobimetallic complexes containing titanium and palladium were prepared from O, N, O- N, N multidentate ligands. The ligands each contained an O, N, O-tridentate part based on a 2,6-lutidine scaffold and an N, N-bidentate di(pyridin-2-yl) part. The O, N, O-moiety selectively coordinated to a titanium atom on treatment with titanium(tetraisopropoxide), although one of the di(pyridin-2-yl) groups in the N, N-moiety coordinated to the titanium atom. The N, N-bidentate di(pyridin-2-yl) moiety coordinated to the palladium atom on treatment with bis(benzonitrile)palladium(II) chloride to afford a heterobimetallic complex. The dynamic behavior of the complexes in solution was studied by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Isodesmosine is a crosslinking pyridinium amino acid of elastin and is an attractive biomarker for the diagnosis of chronic obstructive pulmonary disease (COPD). In this paper, we describe the total synthesis of isodesmosine. The key features of this synthesis are stepwise and regioselective palladium-catalyzed Negishi and Sonogashira cross-coupling reactions for efficient introduction of amino acid segments on the pyridine ring. [ABSTRACT FROM AUTHOR]

Zirconiumcomplexes of some [5]cumulene derivatives were studiedfor their variable coordination modes and haptotropic shifts. Some[5]cumulene compounds reacted with zirconocene(II) species to afford1-zirconacyclopent-3-yne complexes that have five-membered cycloalkynestructures. Only a few [5]cumulene compounds afforded η2-coordinated complexes in the presence of neutral ligandssuch as trimethylphosphine and tert-butyl isocyanide.Interconversion between the five-membered structure and the η2-complex was observed. Investigation of [5]cumulene derivativesof various cycloalkylidene moieties indicated that the η2-complex was preferred when the [5]cumulene has bulkier substituents.A [5]cumulene with 2,2,6,6-tetramethylcyclohexylidene groups muchpreferred the 1-zirconacyclopent-3-yne structure to η2-coordination. In sharp contrast, the η2-coordinatedcomplex was favored for a [5]cumulene with 2,2,7,7-tetramethylcycloheptylidenegroups in the presence of PMe3. Small differences in stericenvironments caused totally different reactivity in [5]cumulene complexes.DFT calculations on the formation enthalpy were consistent with theexperimental results, although that cannot fully rationalize the difference. [ABSTRACT FROM AUTHOR]

The Negishi of an organozinc derivative prepared from protected l-aspartic acid with monohalopyridines was improved by employing a combination catalyst of Pd2(dba)3 and P(2-furyl)3 and removing an extra Zn from the organozinc reagent via centrifugation. The reactivity of halogenated pyridines (Cl, Br, I) with substituents at the C2, C3, and C4 positions of the pyridine ring was investigated, and it was found that the use of 4-iodopyridine as a substrate gave the best yield (90%) for the . [ABSTRACT FROM AUTHOR]

Abstract: Carbon–carbon bond formation reactions of a silyl-substituted [3]cumulene, (Z)-1,4-bis(trimethylsilyl)buta-1,2,3-triene (1), with α,β-unsaturated carbonyl compounds in the presence of Lewis acids are presented. The reactions gave 1,3-enyne compounds bearing a carbonyl moiety, and the silyl groups of 1 were maintained in the products. The reaction of 1,4-dideuterated 1-d 2 suggested that the C–C bond formation proceeds by an ene reaction mechanism. [Copyright &y& Elsevier]

Seven-membered metallacycloalkyne compounds were synthesized. The reaction of the zirconocene-ethylene complex and ( Z)-1,4-bis(trimethylsilyl)buta-1,2,3-triene gave a mixture of 1-zirconacyclopent-3-yne and 1-zirconacyclohept-3-yne. In contrast, zirconocene-alkyne complexes, such as those of 1-(trimethylsilyl)prop-1-yne and diphenylacetylene, gave 1-zirconacyclohept-2-en-5-yne in good yields. Consideration of structural parameters suggests that both a seven-membered cyclic alkyne and a five-membered structure contribute to generation of this complex. Coupling of benzyne and [3]cumulenes on a metal was also found to afford the corresponding metallacycles. [ABSTRACT FROM AUTHOR]

Abstract: O,N,O-tridentate ligands 2-H 2 based on a 2,6-substituted pyridine structure and their dichlorotitanium complexes 3 were synthesized and structurally characterized. The complexes have five-coordinated, trigonal bipyramidal structure, in which one chlorine atom was located at trans-position to the nitrogen atom of the pyridine ring and the other was at cis-position. NMR spectroscopy indicated their fluxional structure in solution. The complexes showed low to modest catalytic activity for ethylene polymerization in the presence of methylaluminoxane (MAO) as a co-catalyst. [Copyright &y& Elsevier]

Abstract: The stereoisomerization of 2,5-disubstituted 1-zirconacyclopent-3-yne compounds, stable five-membered cycloalkynes, has been studied with regard to the mechanism. The bimetallic complex of 1,4-bis(trimethylsilyl)butatriene was synthesized and structurally characterized, although it seems unimportant for the stereoisomerization reactions. The isomerization of trans-1,1-bis(η5-cyclopentadienyl)-2,5-bis(trimethylsilyl)-1-zirconacyclopent-3-yne 2a into the cis-form in benzene-d 6 solution were observed using 1H NMR spectroscopy at 50 °C in various concentrations. The reaction was first order with respect to trans-2a. This ruled out the possibility that a bimetallic complex was responsible for the isomerization. A kinetic isotope effect was observed (k H/k D = 1.8), suggesting that C–H activation is involved in the rate-determining step. A mechanism via hydrogen elimination from the complex of η4-π,π-coordination mode is proposed. [Copyright &y& Elsevier]

A five-membered metallacycloallene complex, 1-zirconacyclopenta-2,3-diene, was prepared from low-valent zirconocene and 2,4-bis(trimethylsilyl)but-1-en-3-yne. The complex reacted with carbonyl compounds to afford alkynyl alcohols after hydrolysis via C=O insertion into Zr-C bond. Similarly, nitriles inserted into the Zr-C bond to give the corresponding ketones after hydrolysis. The insertion of C=O and CN selectively took place at zirconium-sp³ carbon of the metallacycle. [ABSTRACT FROM AUTHOR]

The Eisomer of a [5]cumulene derivative, 2,2,9,9-tetramethyl-3,8-diphenyldeca-3,4,5,6,7-pentaene (1), which was previously believed to be unisolable owing to very fast E/Zisomerization, was isolated and structurally characterized. The Zisomer was trapped as the transition-metal complex 5, and the molecular structure was determined. DFT calculations and an electrochemical study on 1are also described. [ABSTRACT FROM AUTHOR]

Five-membered metallacycloallene compounds, 1-zirconacyclopenta-2,3-dienes 1 , derived from but-1-en-3-ynes 2 and low-valent zirconocene, reacted with esters and isocyanates. Reactions of 1 with carboxylic esters such as ethyl acetate and methyl benzoate resulted in the formation of alkynyl ketones after hydrolysis, albeit in low yields, and diethyl carbonate gave alkynyl esters in moderate yields. Insertion of isocyanates such as phenylisocyanate to the Zr–C bond of 1 afforded an alkynyl amide when 1 had substituents at the 2,4-positions (1a), while the zirconium complexes 1 that had silyl groups at the 2,5-positions, 1b and 1c , gave dienyl amides after hydrolysis. These reactions involved C O insertion into the Zr-C sp 3 bond in 1. It is likely that the insertion afforded seven-membered 1-oxa-2-zirconacyclohepta-3,4-diene intermediates first, whilst the reaction of 2,5-disilyl-1-zirconacyclopenta-2,3-dienes 1b-c with isocyanates formed five-membered 1-oxa-2-zirconacyclopent-3-ene intermediates. Additional C–C bond formation reactions of these intermediates via transmetallation to copper salts followed by addition of allyl halides furnished allylated products. Image 1 • The reactivity of five-membered zirconacycloallene complexes prepared from zirconocene and 1,3-enyne was studied. • The 1-zirconacyclopenta-2,3-diene complexes reacted with diethyl carbonate to give the alkynyl esters after hydrolysis. • The 2,4 -disilyl-1-zirconacyclopenta-2,3-dienes reacted with isocyanates to give an alkynyl amide after hydrolysis • The 2,5 -disilyl-1-zirconacyclopenta-2,3-diene reacted with isocyanates to give dienyl amides after hydrolysis. • Allylation of the intermediate promoted by copper salt, instead of hydrolysis, provided allylated products. [ABSTRACT FROM AUTHOR]

The palladium-catalyzed Negishi cross-coupling reaction is improved by using Pd2(dba)3 and P(2-furyl)3 as the catalyst system and by removing both the undesired Zn(II) species and the insoluble Zn metal from the activated organozinc reagent via centrifugation. [ABSTRACT FROM AUTHOR]

The reaction proceeds without cleavage of the C-Si bond. [ABSTRACT FROM AUTHOR]

The cover picture shows the coupling of an alkyne and [3]cumulene on a zirconium atom to form a seven‐membered metallacycloalkyne and a five‐membered metallacyclic complex. The reaction is reminiscent of an imaginary Chinese creature, The Black Tortoise (Xuanwu; “Genbu” in Japanese), in which a snake coils around a tortoise. Both the tortoise and the snake are looking at a sphere, which represents a zirconium atom, in a way similar to how the alkyne and the [3]cumulene interact with the metal. The background shows the sunrise at New Year taken from the ruins of Ichiya Castle at Odawara. Details are discussed in the article by N. Suzuki et al. on p. 347 ff. [ABSTRACT FROM AUTHOR]

Invited for this month's cover is the group of Noriyuki Suzuki at Sophia University. The image shows how [3]comulene couples with an alkyne on the zirconium atoms. It is interesting that replacing one carbon atom with zirconium makes the cycloalkyne so stable... Read more about the story behind the cover in the Cover Profile and about the research itself on p. 347 ff. [ABSTRACT FROM AUTHOR]