Π-allylpalladium Complexes Research Articles

Palladium-catalyzed oxaspirocyclizations

Palladium-catalyzed oxidation of 1-(3-hydroxyalkyl) and 1-(4-hydroxyalkyl)-1,3-cycloalkadienes results in a stereocontrolled oxaspirocyclization. The reaction proceed via a spirocyclic (π-allyl)palladium intermediate, which is attacked by an acetate or a chloride nucleophile leading to an overall 1,4-addition across the diene. The intermediate (π-allyl) palladium complex was independently prepared and characterized. The stereochemistry of the 1,4-addition can be controlled to give either cis or trans 1,4-addition across the double bonds. The oxaspirocyclization was applied to the total synthesis of theaspirone.

Palladium-catalyzed Carbonylation of Allylamines. Synthesis of β,γ-unsaturated amides by one-carbon homologation of Allylamines

Palladium-catalyzed carbonylation of allylamines under CO (50atm) at 110°C proceeds highly efficiently to give the corresponding β,γ-unsaturated amides. The carbonylation occurs at the less substituted carbon of allyl units to give linear amides with high regioselectivity. The reaction can be rationalized by assuming the mechanism which involves oxidative addition of palladium (0) species to allylamines to give π-allylpalladium complexes, insertion of carbon monoxide to give acylpalladium species, and amidation.

Synthesis of bicyclic nitrogen compounds via tandem intramolecular Heck cyclization and subsequent trapping of intermediate .pi.-allylpalladium complexes

Intramolecular palladium-mediated three-component cyclizations of substrates containg vinyl halide, olefin, and sulfonamide moieties to generate a diverse group of nitrogen heterocycles have been developed. The methodology has been applied to construction of both fused and bridged bicyclic systems. The strategy can also be used for spirocyclizations. This chemistry involves regiospecific generation of π-allylpalladium complexes via Heck reactions of vinyl halides and simple olefins, followed by nucleophilic addition of sulfonamide anions to these intermediates

New ring-opening polymerization via a .pi.-allylpalladium complex. 2. Novel proton-transfer polymerization of vinylcyclopropane derivatives having two electron-withdrawing substituents

Vinylcyclopropane derivatives having two electron-withdrawing groups such as ethoxycarbonyl, cyano, and phenylsulfonyl on the cyclopropane rings, were polymerized in the presence of a Pd(O) catalyst. Both the vinyl group and the cyclopropane ring participated in the polymerization with ring opening. The key intermediate of the polymerization is a π-allylpalladium complex which is generated by the oxidative addition of a Pd(O) complex to the monomer. The propagating end is a methyne proton activated by two electron-withdrawing substituents. The polymerization proceeds via novel intermolecular proton transfer through the π-allylpalladium complex

パラジウム触媒を用いる新しいタイプの重合反応

It has been well documented that palladium complexes catalyze versatile and useful reactions. Contemplation of these reactions from the standpoint of polymer synthesis has brought new polymerizations, which are reviewed in this article including topics of ring-opening polymerization, polycondensation, polyaddition, and addition polymerization. 1) A new type of ring-opening polymerization, whose key intermediates were π-allyl palladium complexes, was developed. Especially, for the polymerization of cyclic carbamates was designed and achieved an unusual mode that propagating ends multiply at every step of propagation. The produced polyamines had hyperbranched dendritic structures incorporating the initiator as the core. 2) Aromatic polymers such as poly (phenylene vinylene) s, polyphenylenes, and polyamides were prepared by the Heck reaction and Pd-catalyzed cross-coupling reactions. 3) Electrophilic palladium complexes initiated vinyl polymerizations of styrene, methyl propiolate, norbornene, etc. as well as alternating copolymerizations of some alkenes with carbon monoxide. Bromo (methyl) palladium-phosphine complexes initiated living aromatization polymerizations of 1, 2-diisocyanoarenes. 4) A cyclic compound having a Si-Si bond, 1, 2-disilacyclopentane, was polymerized with the aid of a Pd (0) complex.

Cyclopropanes via nucleophilic attack at the central carbon of (π-allyl)palladium complexes

A variety of carboanions (pKa of protonated carbanion 20) combine with (π-allyl)palladium complexes in the presence of N, N, N′, N′, tetramethylethylenediamine (TMEDA)via a new reaction mode, giving functionalized cyclopropanes.

Electronic effects in the regioselectivity of nucleophilic attacks on cationic 1,3-diaryl-π-allylpalladium complexes

Nucleophilic attacks on π-allylpalladium complexes derived from O 2NPh(CHCHCH)PhX systems (X = 4-OMe and 4-Cl) occur prefentially at the allylic terminus remote from the electron-withdrawing group (NO 2).

π‐アリルパラジウム錯体の見かけ上の電荷反転 アリルアルコール類によるカルボニル‐アリル化反応への応用

Palladium-catalyzed carbonyl allylation by allylic alcohols with SnCl2 smoothly proceeds in aqueous medium under air. The actual allylating agent in the carbonyl allylation by allyl alcohol in dry medium is allyltrichlorotin, which is prepared via (1) oxidative addition of allyl alcohol to Pd (0) complex with SnCl2, (2) insertion of SnCl2 to π-allylpalladium complex, followed by (3) reductive elimination of π-allylpalladium trichlorostannate. Allylic alcohols, preparing π-allylpalladium complexes, function as synthons of allylic carbanions. In other words, this implies the apparent charge reversal of electrophilic π-allylpalladium complexes. The carbonyl allylation by allylic alcohols can achieve high chemo-, regio-, and diastereoselection by the choice of solvent, and can be applied to chelation-controlled diastereoselection in polar solvents.

Stereochemistry of the palladium-catalyzed allylic substitution: the syn-anti dichotomy in the formation of (π-allyl)palladium complexes and their equilibration

The mechanism of palladium(0)-catalyzed allylic substitution has been investigated with the aim of finding whether or not the intermediate (π-allyl)palladium complexes can arise in a syn fashion as an alternative to the well known anti-mechanism. Using (diphenylphosphino)acetate as a leaving group and stereochemically biased substrates 30b and 35b evidence for the syn stereochemistry has been acquired ( 30b → 31 and 35b → 36). This reversal of stereochemistry is facilitated by severe steric congestion in the starting allylic esters (which impairs the ordinary anti-mechanism) and is boosted by the pre-coordination of the Pd(0) reagent to the leaving group. The latter effect apparently lowers the activation entropy. With cyclohexene derivatives 10b, 18b, and 19b and acyclic substrate 25b, where steric hindrance does not operate, the anti-mechanism producing η 3-complexes dominates even for (diphenylphosphino)acetates. At elevated temperature, rapid equilibration of η 3-complexes ( 13 ⇄ 14 and 20 ⇄ 21) has been observed prior to the reaction with a nucleophile. This effect has been attributed to the presence of (diphenylphosphino)acetate ion acting as a ligand for palladium.

Carbopalladation of functionalized allenes : regioselectivity of the reaction of carbonucleophiles with the intermediate π-allyl palladium complexes.

A methoxy group orients the carbonucleophile onto the oxygen-substituted secondary carbon. Carbopalladation of functionalized allenes leads to π-allyl palladium complexes, the regiochemistry of which towards carbonucleophiles has been studied : a methoxy group has been demonstrated to reverse the classical regioselectivity and to allow the formation of the more substituted product.

Stereospecific reduction and cross-coupling of .gamma.-monosubstituted allylic chlorides using coordinatively unsaturated palladium catalysts

In stereospecific reduction of (E)- and (Z)-γ-monosubstituted allylic chlorides has been accomplished via low-temperature hydride capture of the corresponding π-allylpalladium complexes. In addition, cross-coupling of a (Z)-γ-monosubstituted allylic chloride with an organometallic reagent has been achieved without loss of double bond geometry. Key to these processes is the use of reactive, coordinatively unsaturated palladium species which promote C-H and C-C bond forming reactions prior to isomerization of the allylic double bond. Although the latter process furnishes predominantly «head to head» coupled products, formation of regioisomers remains a problem

Structure and reactivity of cis- and trans-bis-[{5-carbomethoxy-(1,2,3-η)-cyclohexenyl}palladium]. Evidence for a (σ-allyl)palladium intermediate in the cis-migration of acetate from palladium to coordinated π-allyl

The mode of attack by acetate on a (π-allyl)palladium complex depends not only on the ligands on palladium, but also on the structure of the complexes; for the bis-[{5-carbomethoxy-(1,2,3-η3)-cyclohexenyl}palladium] complexes, the structures of which were determined by X-ray crystallography and NMR spectroscopy, the cis isomer preferably reacted by external attack whereas the trans isomer, under identical conditions, preferred internal migration.

Asymmetric induction reactions. IV. Palladium-catalyzed asymmetric allylations of chiral enamines bearing phosphine groups.

The palladium-catalyzed asymmetric allylations of chiral enamines, derived from (S)-2-(diphenylphosphinomethyl)pyrrolidine, produced optically active α-allyl carbonyl compounds in high optical yields. The phosphino group in the chiral enamines presumably serves as a chiral ligand in these palladium-catalyzed reactions. In the transition states of π-allylpalladium complexes coordinated with the intramolecular phosphine group, the anionic counterparts or allylating reagents are considered to play an important role in controlling of the grade of the enantioselectivity.

ChemInform Abstract: Selectivities in Organic Reactions via π‐Allylpalladium Complexes

ChemInformVolume 21, Issue 16 Reviews ChemInform Abstract: Selectivities in Organic Reactions via π-Allylpalladium Complexes J. TSUJI, J. TSUJI Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Meguro, Tokyo 152, JapanSearch for more papers by this author J. TSUJI, J. TSUJI Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Meguro, Tokyo 152, JapanSearch for more papers by this author First published: April 17, 1990 https://doi.org/10.1002/chin.199016372Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue16April 17, 1990 RelatedInformation

Expanding Industrial Applications of Palladium Catalysts

Rapidly expanding industrial applications of palladium catalysts as homogeneous and heterogeneous catalysts are surveyed. They are classified into two types. The first type includes the oxidative reactions of olefins and aromatic compounds, and oxidative carbonylation. These reactions are catalyzed by Pd(II) salts and appropriate reoxidants. Reactions catalyzed by Pd(0) complexes are the second type, which includes reactions of organic halides and reactions via π-allylpalladium complexes. Also some promising palladium-catalyzed reactions, which may be used in commercial processes in future, are included. 1. Introduction 2. Oxidative Reactions Catalyzed by Pd(II) Salts 2.1. Oxidative Reactions of Olefins 2.2. Oxidative Reactions of Aromatic Compounds 2.3. Oxidative Carbonylation and Other Reactions 2.4. Summary 3. Reactions Catalyzed by Pd(0) Complexes 3.1. Reactions of Alkenyl and Aryl Halides 3.2. Catalytic Reactions of Allylic Compounds and Conjugated Dienes via π-Allylpalladium Complexes 3.3. Carbonylation of Olefins 4. Concluding Remarks

Solvent Effects in 1H-NMR Spectrum of Steroidal π-Allyl Palladium Chloride Complexes

Abstract The 1H-NMR spectra of the steroidal α-π-allyl palladium complexes in which palladium coordinated at the α-face showed higher field shift of C-19 methyl signal in C6D6 than in the case of CDCl3. The configuration of palladium in π-allyl palladium complexes was confirmed by this phenomenon.

Electronic effects on the regioselectivity of nucleophilic attacks on π-allylpalladium complexes

A high regioselectivity has been observed in the palladium catalyzed allylation of “soft” nucleophiles (pentane-2,4-dione and 4-hydroxy-6-methyl-2-pyrone) when both allylic termini have the same steric requirements and different electronic features.

Insertion of carbon monoxide into a palladium–allyl bond

Trimethylphosphine-co-ordinated π-allylpalladium complexes [(π-allyl)Pd(PMe3)2]X(X = halide) undergo CO insertion into the palladium–allyl bond to give 3-butenoylpalladium complexes under mild conditions.

Palladium-assisted route to carbocyclic nucleosides: A formal synthesis of (±)-aristeromycin

The carbocyclic nucleoside aristeromycin ( 1) has been formally synthesized from cyclopentadiene monoepoxide ( 4) via the sequential generation of cationic (π-allyl)palladium complexes.

Synthesis of silylated 1,3-dienes via the carbopalladation of allenes.

Catalytic carbopalladation of allenes 1 or 2 with silylated vinyl bromides 3 gives π-allyl palladium complexes 5 which are trapped by stabilized enolates and lead to β-difunctionalized silylated dienes 7 – 9 .