Practical Stannylation of Allyl Acetates Catalyzed by Nickel with Bu3SnOMe

A practical and scalable nickel‐catalyzed allylic stannylation of allyl acetates with Bu₃SnOMe is described. A variety of acyclic and cyclic allyl acetates, even with base‐sensitive moieties, undergoes the stannylation by using NiBr₂/4,4′‐di‐tert‐butylbipyridine (dtbpy)/Mn catalyst system to afford highly functionalized allyl stannanes with excellent regioselectivity and yields. Furthermore, the scope of protocol is also extended by the reaction of propargyl acetates, giving rise to propargyl or allenyl stannanes. Additionally, a unique diastereoselectivity using the nickel catalyst different from the palladium was demonstrated for the stannylation of cyclic allyl acetates. In the reaction, inexpensive and stable nickel complexes, abundant reductant (Mn), and atom‐economical stannyl source were used.     

Ruthenium‐Catalyzed Oxidant‐Free Allylation of Aromatic Ketoximes with Allylic Acetates at Room Temperature

Substituted aromatic ketoximes reacted efficiently with allylic acetates in the presence of {[RuCl₂(p‐cymene)]₂} and AgSbF₆ in 1,2‐dichloroethane at ambient temperature, providing ortho‐allyl aromatic ketoximes in a highly regioselective manner without an oxidant. In the reaction, the acetate group of allyl acetate acts as a base to activate the C?H bond of aromatics. Later, ortho‐allyl aromatic ketoximes were converted into ortho‐allyl aromatic ketones in the presence of HCl.     

Palladium(O)-promoted synthesis of functionally substituted allenes by means of organozinc compounds

The paper describes new routes to aryl-, vinyl-, and 1-alkynylallenes and to diallenes $\text{via}$ Pd(PPh₃)₄-promoted reaction of propargylic or allenic halides with appropriate organozinc halides. Propargylic acetates are also suited to prepare such allenes.     

Isoerization of allylic acetates catalyzed by palladium. New method for stereocontrol.

Reaction of allylic acetates with tetrakis (triphenylphosphine) palladium leads to positional and stereochemical isomerism. A mechanism is proposed. Elimination of allyl acetates to dienes is also observed and constitutes a useful synthetic procedure. The use of bis(benzenesulfonyl)methane as a ^ΘCH₂^Θ equivalent is reported.     

Double amination of 2-fluoroallylic acetates by palladium catalysts

We accomplished the palladium-catalyzed double substitution of 2-haloallylic acetates with nitrogen nucleophiles. During the Pd₂(dba)₃/DPPE-catalyzed reaction of 2-fluoroallylic acetates with N-substituted-p-toluenesulfonamide, two equivalents of nitrogen nucleophiles were introduced to the allyl unit with a Z-selectivity through the carbon–fluorine bond cleavage. We further demonstrated the reaction of 2-chloroallylic acetates, and succeeded in obtaining the same doubly-substituted products in good yields with a high Z-selectivity.     

Transition metal σ-complexes in organic synthesis. 4. Cross coupling of allyl esters and allyl aryl sulfones with organotitanium compounds in the presence of palladium complexes

Conclusions The reactions of organotitanium compounds PhTi(OPr-i)₃ and MeTi(OPr-i)₃ with allyl acetates, allyl phenyl ethers, allyl aryl sulfones, and allylic tosylates and mesylates are catalyzed by Pd complexes and lead to the formation of cross-coupling products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2159–2166, September, 1988.     

Palladium-catalyzed and samarium-promoted coupling of stereochemically-biased allylic acetates with carbonyl compounds

Stereochemically-biased bicyclic allylic acetates endo- and exo-1 were shown as being allyl donors for Pd-catalyzed carbonyl allylation using stoichiometric quantities of samarium diodide. Cyclopentenyl acetate and bicyclic derivatives 1 react with cyclic ketones in the presence of SmI₂ without requirement of palladium catalysis. Use of enantiomerically enriched substrate suggests that the reaction goes through a π-allyl samarium complex. However, this reactivity appears to be restricted to strained cyclopentenyl acetates since other linear and cyclic allylic acetates do not give the carbonyl allylation product.     

Gold(I)-catalyzed intermolecular hydroarylation of allenes with nucleophilic arenes: scope and limitations

The addition of nucleophilic methoxyarenes to allenes proceeds at room temperature in dichloromethane with a catalytic amount of phosphite-gold(I) precatalyst and silver additive. The addition is regioselective for the allene terminus, and generates E-allylation products without the need for prefunctionalization of the synthons as organometallics or allyl bromides. Coordinating heteroaromatics and sterically hindered allenes do not participate in the reaction.     

Preparation of substituted allyl acetates and sulfones from Baylis-Hillman adducts in ionic liquid media

Reactions of potassium acetate and the sodium salt of p-toluenesulfinic acid with acetates of Baylis-Hillman adducts produce substituted allyl acetates and allyl sulfones respectively. Ionic liquids are utilized in place of conventional solvents.     

Iodine-Mediated One-Pot Synthesis of 1,4,5-Substituted Pyrazoles from MBH Acetates via Allyl Hydrazone Intermediate

Herein, we report the regioselective one-pot synthesis of 1,4,5-trisubstituted pyrazoles by reacting Morita-Baylis-Hillman (MBH) acetates derived from aryl aldehydes with alkyl or aryl hydrazines in the presence of iodine under aerobic conditions. The reaction proceeds through sequential S_N2′ nucleophilic substitution of substituted hydrazine onto the MBH acetate, I₂-catalyzed oxidation of the allylic hydrazine to allylic hydrazone, heating-induced intramolecular aza-Michael reaction and cyclization, and oxidative aromatization. The key intermediate, the s-trans allyl hydrazones were isolated in good yields by performing the reactions at room temperature. However, the allyl hydrazones prepared from the MBH acetates of aliphatic aldehydes did not furnish the pyrazole owing to the absence of an activated methylene group in the substrate. The synthetic applications of the pyrazoles in Ugi reactions, decarboxylative halogenation, Pd-catalyzed benzoylation of the N-aryl ring, and metal-free tetrazole synthesis has been demonstrated.     

Copper‐Catalyzed Borylative Allyl–Allyl Coupling Reaction

Borylative allyl–allyl coupling using allenes, bis(pinacolato)diboron, and allyl phosphates has been developed in the presence of a copper catalyst bearing an N‐heterocyclic carbene ligand. The reaction affords boryl‐substituted 1,5‐diene derivatives in good to high yields with high regioselectivity and Z selectivity.     

Stereoselective Synthesis of (Z)‐ and (E)‐Allyl Aryl Sulfides and Selenides from Baylis?Hillman Acetates under Neutral Conditions Using β‐Cyclodextrin in Water

The first example of the stereoselective synthesis of (Z)‐ and (E)‐allyl aryl sulfides and selenides from Baylis? Hillman acetates under neutral conditions in H₂O by supramolecular catalysis involving β‐cyclodextrin is reported. β‐Cyclodextrin can be recovered and reused. The reaction is very efficient in providing allyl aryl sulfides and selenides in good‐to‐excellent yields with clean reaction profiles under mild reaction conditions.     

Palladium-catalyzed cross-coupling reaction of allyl acetates with pinacol aryl- and vinylboronates

Pinacol boronates 2 couple efficiently with allyl acetates 1 in the presence of a palladium catalyst prepared in situ from PdCl₂ and TFP to give the coupled products 3 in moderate to good yields under mild conditions.     

Scope of the palladium-catalyzed coupling reaction of organometallics with allylic electrophiles. Effect of the leaving group

Various allyl alcohol derivatives containing OAlR₂, OPO(OR)₂, and OSiR₃ groups, in addition to allylic halides and acetates, participate in the Pd-catalyzed coupling reaction with alkenyl- and arylmetals, such as those containing Al, Zn and Zr.to give the corresponding cross-coupled products, the order of their reactivity being: halogen, OAc > OAlR₂ > OPO(OR)₂ > OSiR₃.     

Synthesis of Allyl Aryl Sulfone Derivatives from Baylis?Hillman Acetates in Water

Various phenyl and p‐tolyl allyl sulfone derivatives were prepared stereoselectively by reacting Baylis? Hillman acetates with sodium 4‐R‐benzenesulfinate (R=H, Me) in H₂O. The reaction was very efficient in providing the corresponding sulfone derivatives in good to excellent yields (Table).     

Heterogeneous Copper-Catalyzed Cross-Coupling for Sustainable Synthesis of Chiral Allenes: Application to the Synthesis of Allenic Natural Products

Classical Crabbé type S_N2' substitutions of propargylic substrates has served as one of the standard methods for the synthesis of allenes. However, the stereospecific version of this transformation often requires either stoichiometric amounts of organocopper reagents or special functional groups on the substrates, and the chirality transfer efficiency is also capricious. Herein, we report a sustainable methodology for the synthesis of diverse 1,3-di and tri-substituted allenes by using a simple and cheap cellulose supported heterogeneous nanocopper catalyst (MCC-Amp-Cu(I/II)). This approach represents the first example of heterogeneous catalysis for the synthesis of chiral allenes. High yields and excellent enantiospecificity (up to 97 % yield, 99 % ee) were achieved for a wide range of di- and tri-substituted allenes bearing various functional groups. It is worth noting that the applied heterogeneous catalyst could be recycled at least 5 times without any reduced reactivity. To demonstrate the synthetic utility of the developed protocol, we have applied it to the total synthesis of several chiral allenic natural products.     

Catalytic hydroallylation of norbornadiene with allyl formate

Norbornadiene (NBD) reacts with allyl esters All—OC(O)R (R = Me, Bu^t, Ph, CCl₃, CF₃) in acetonitrile solutions of palladium(0) complexes to give a mixture of four isomeric nontraditional allylation products and the corresponding carboxylic acids. Under similar conditions, the reaction of NBD with allyl formate in solutions of Pd⁰ and Pd^II complexes occurs selectively, resulting in the product of addition of the allyl fragment and the H atom to an NBD double bond, 5-allylbicyclo[2.2.1]hept-2-ene, and CO₂. The hydroallylation of NBD is accompanied by catalytic addition of formic and acetic acids to one double bond of the diene to give bicyclo[2.2.1]hept-2-en-5-ol and nortricyclan-3-ol acetates and formates. Unlike most known palladium-based catalyst systems, these complexes exhibit catalytic activity also in the absence of phosphines. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 309–313, February, 2007.     

Stereoselective synthesis of trisubstituted alkenes containing (Z)‐allylthio units from the acetates of Baylis–Hillman adducts

A series of trisubstituted alkenes containing (Z)‐allylthio moieties as key structural units, that is, sodium (Z)‐allyl thiosulfates, symmetrical di(Z‐allyl) sulfides, and di(Z‐allyl) disulfides, unsymmetrical diallyl sulfides were prepared in moderate to good yields via chemical transformations from the acetates of Baylis‐‐Hillman adducts. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:188–198, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20394     

Palladium catalyzed three component coupling reaction between chromones, alcohols, and allylic acetates: diversity-oriented synthesis of highly substituted chromones

This paper describes the palladium catalyzed highly efficient three component coupling (TCC) reactions between chromones, allylic acetates, and alcohols, which lead to a library of multiply substituted chromones. The activity of various palladium catalysts, such as Pd(PPh₃)₄ and Pd₂dba₃·CHCl₃ and their combination with various bisphosphine ligands, was investigated by using THF as a solvent, which revealed that Pd(PPh₃)₄ catalyst was the best one. The reaction most probably proceeds via the formation of benzopyrilium cation, generated from the reaction between chromones and allyl acetate, in the presence of palladium catalyst. The subsequent trapping of the benzopyrilium cation by alcohols would give the corresponding products in excellent yields. This alkoxy-allylation reaction was highly diastereoselective and only one diastereomer was obtained in all the cases.     

Boraformylation and Silaformylation of Allenes

The boraformylation of allenes with B₂(pin)₂ and a formate ester as boron and formyl source, respectively, proceeds in the presence of a copper catalyst. The reaction selectively affords the corresponding β‐boryl β,γ‐unsaturated aldehydes in good to high yields. Furthermore, the silaformylation of allenes was achieved with a formate ester and PhMe₂Si−B(pin) as the silicon source.