Studies on t-BuOK-catalyzed Michael addition of 1,2-allenic ketones with 2-substituted diethyl malonates: highly selective synthesis of β,γ-unsaturated enones

In this paper, we have demonstrated a facile nucleophilic addition of 2-substituted diethyl malonate to various substituted 1,2-allenic ketones to afford β,γ-unsaturated enones using a catalytic amount of t-BuOK as the base. The reaction usually completes within 10 min in acetone at room temperature. The stereoselectivity of the reaction with γ-substituted allenic ketones is very high affording the β,γ-unsaturated E-enones.     

1,2-联烯基酮的合成与反应

1,2-联烯基酮可以通过2-丙炔基酮异构化反应,相应有机金属试剂中间体与酯、酰氯或酰胺的反应,[2,3]或[3,3]迁移反应,Wittig反应,消除反应,2,3-联烯醇氧化等方法合成。由于联烯酮上含有吸电子基团羰基,它可发生亲核加成、环加成、环化反应。     

Ru(III)-catalyzed oxidation of homopropargyl alcohols in ionic liquid: an efficient and green route to 1,2-allenic ketones

An efficient and environmentally benign synthesis of 1,2-allenic ketones via RuCl₃-catalyzed oxidation of homopropargyl alcohols in ionic liquid with tert-butyl hydroperoxide (TBHP) as the oxidant was reported for the first time. With its reasonable efficiency and green nature, this oxidation provides a novel alternative route to 1,2-allenic ketones.     

Pd0-catalyzed coupling cyclization reaction of Aryl or 1-alkenyl halides with 1,2-allenyl ketones: scope and mechanism. An efficient assembly of 2,3,4-, 2,3,5-tri- and 2,3,4,5-tetrasubstituted furans

Described herein is the Pd(0)-catalyzed coupling cyclization reaction of 1,2-allenyl ketones with organic halides leading efficiently and conveniently to not only 2,3,4- and 2,3,5-trisubstituted furans but also 2,3,4,5-tetrasubstituted furans. Furthermore, this method showed high substituent-loading capability and tolerance of various substituents. The reactions of 1,2-allenyl ketones 1 e, 1 p, 1 q, and deuterated [D]1 c were performed for a mechanistic study, which demonstrated that instead of an enolization pathway, the reaction may proceed via the intermediacy of dienolate palladium and intramolecular nucleophilic attack on the pi-allyl palladium intermediate by the carbonyl oxygen.     

Pd(CH3CN)2Cl2-catalyzed oxidative heterodimerization reaction of 2,3-allenamides and 1,2-allenyl ketones: an efficient synthesis of 4-(furan-3'-yl)-2(5H)-furanimines

The Pd(II)-catalyzed oxidative heterodimerization reaction of 2,3-allenamides and 1,2-allenyl ketones was studied. It provides an efficient route for the synthesis of the polysubstituted 4-(furan-3'-yl)-2(5H)-furanimines, which are not readily available from the known methods. Due to the application of benzoquinone, the loadings of both the palladium catalyst and ketone have been greatly reduced for the oxidative heterodimerization of 2,3-allenamides and 1,2-allenyl ketones in acetic acid.     

Gold-catalyzed synthesis of polycyclic enones from carbon tethered 1,3-enynyl carbonyls via tandem heteroenyne metathesis and Nazarov reaction

An efficient and general Au(III)-catalyzed tandem reaction, heteroenyne metathesis and Nazarov cyclization, of 1,3-enynyl ketones to produce fused tri- and tetracyclic enones has been developed. The products were formed with excellent regioselectivity of the double bond position and with very high diastereoselectivities. In this reaction, the Au(III) catalyst exhibits dual roles for activating both alkynes and carbonyls.     

Sc(OTf)3-catalyzed indolylation of 1,2-allenic ketones: controlled highly selective synthesis of beta-indolyl-alpha,beta-unsaturetated (E)-enones and beta,beta-bisindolyl ketones

[reaction: see text] A novel highly stereoselctive synthesis of beta-indolyl-alpha,beta-unsaturated (E)-enones by the hydroindolylation of the beta,gamma-C=C bond of 1,2-allenic ketones in the presence of 5 mol % Sc(OTf)(3) was developed. beta,beta-Bisindolyl ketones were prepared by using 2.5 equiv of indoles. A stepwise protocol for introducing different indoles was also established.     

Efficient synthesis of 4-(3'-furanyl)butenolide derivatives via PdII-catalyzed oxidative heterodimeric cyclization reaction of 2,3-allenoic acids and 1,2-allenyl ketones

The oxidative cyclization/dimerization reaction between two classes of allenes with different functionalities was reported to provide an efficient route to polysubstituted 4-(3'-furanyl)-2(5H)-furanones, which are not readily available from the known methods. The highly optically active butenolides could be easily formed from the optically active 2,3-allenoic acids, which was obtained conveniently through chiral resolution with optically active amines, that is, cinchonidine or alpha-methyl benzylamine. A mechanistic study showed that the reaction proceeded via a matched double oxypalladation-reductive elimination process. The Pd(II) species may be regenerated via the subsequent cyclometallation of two equivalents of 1,2-allenyl ketones with Pd(0) and protonlysis of Pd enolates formed with the in situ generated HCl.     

Palladium-catalyzed decarboxylation of allenyl 3-oxoalkanoates: an efficient synthesis of 3,4-allenyl ketones

An efficient synthesis of 3,4-allenyl ketones via the Pd-catalyzed decarboxylative coupling of the readily available 3-oxoalkanoates is reported. The C-C bond forming reaction occurs under mild conditions producing CO(2) as the only byproduct.     

Palladium-catalyzed cyclization reaction of allylic bromides with 1,2-dienyl ketones. An efficient synthesis of 3-allylic polysubstituted furans

3-Allylic polysubstituted furans were synthesized via a palladium-catalyzed cyclization reaction of allylic bromides with differently substituted 1,2-allenyl ketones. This process may occur via the reaction of a furanyl palladium intermediate with allylic bromide.     

Tandem reactions of 1,2-allenic ketones leading to substituted benzenes and α,β-unsaturated nitriles

One-pot double Michael addition/intramolecular aldol reaction/decarboxylation of 1,2-allenic ketones with cyanoacetate offers an efficient and convenient approach to highly functionalized benzenes. With 2-substituted cyanoacetates, the reaction proceeds via a different tandem process to afford α,β-unsaturated nitriles effectively.     

Solvent-free reactions of C60 with active methylene compounds, either with or without carbon tetrabromide, in the presence of bases under high-speed vibration milling conditions

Solvent-free reactions of C(60) with active methylene compounds, either with or without carbon tetrabromide (CBr(4)), in the presence of a base under high-speed vibration milling (HSVM) conditions were investigated. The reaction of C(60) with diethyl bromomalonate was conducted under HSVM conditions in the presence of piperidine, triethylamine or Na(2)CO(3) to afford cyclopropane derivative. In the presence of CBr(4), methanofullerenes, and could be obtained by the direct reaction of C(60) with diethyl malonate, dimethyl malonate, ethyl acetoacetate and ethyl cyanoacetate, respectively, with the aid of 1,8-diazabicyclo[5,4,0]undec-7-ene, piperidine, triethylamine or Na(2)CO(3). More interestingly, 1,4-bisadducts and were produced by the reaction of C(60) with diethyl malonate and dimethyl malonate in the presence of piperidine, triethylamine or Na(2)CO(3) under HSVM conditions. On the other hand, dihydrofuran-fused C(60) derivatives, and were obtained from the reaction of C(60) with ethyl acetoacetate, 2,4-pentanedione and 5,5-dimethyl-1,3-cyclohexanedione with the aid of a base. Under the same conditions, less activated aryl methyl ketones such as 2-acetylpyridine, 2-acetylpyrazine and acetophenone provided monocarbonylated methanofullerene derivatives, and. Except for the Bingel reactions, all other reactions under the HSVM conditions are considered to proceed according to a single-electron-transfer mechanism.     

Diene hydroacylation from the alcohol or aldehyde oxidation level via ruthenium-catalyzed C-C bond-forming transfer hydrogenation: synthesis of beta,gamma-unsaturated ketones

Under the conditions of ruthenium-catalyzed transfer hydrogenation, isoprene couples to benzylic and aliphatic alcohols 1a-g to deliver beta,gamma-unsaturated ketones 3a-g in good to excellent isolated yields. Under identical conditions, aldehydes 2a-g couple to isoprene to provide an identical set of beta,gamma-unsaturated ketones 3a-g in good to excellent isolated yields. As demonstrated by the coupling of butadiene, myrcene, and 1,2-dimethylbutadiene to representative alcohols 1b, 1c, and 1e, diverse acyclic dienes participate in transfer hydrogenative coupling to form beta,gamma-unsaturated ketones. In all cases, complete branch regioselectivity is observed, and, with the exception of adduct 3j, isomerization to the conjugated enone is not detected. Thus, formal intermolecular diene hydroacylation is achieved from the alcohol or aldehyde oxidation level. In earlier studies employing a related ruthenium catalyst, acyclic dienes were coupled to carbonyl partners from the alcohol or aldehyde oxidation level to furnish branched homoallylic alcohols. Thus, under transfer hydrogenative coupling conditions, all oxidation levels of substrate (alcohol or aldehyde) and product (homoallyl alcohol or beta,gamma-unsaturated ketone) are accessible.     

K(2)CO(3)-catalyzed Michael addition-lactonization reaction of 1,2-allenyl ketones with electron-withdrawing group substituted acetates. An efficient synthesis of alpha-pyrone derivatives

[reaction: see text] Alpha-pyrone derivatives were synthesized via the base catalyzed or promoted reaction of 1,2-allenyl ketones and electron-withdrawing group substituted acetates. The reaction was believed to proceed through a Michael addition C-C double-bond migration-lactonization process.     

Diversified assembly of perfluoroalkyl-substituted furans and 2,5-dihydrofuran-2-ols

We have developed a facile and effective synthesis of 3-iodofurans from 3-monosubstituted 1,2-allenyl perfluoroalkyl ketones or 2-hydroxy-4-iodo-2,5-dihydrofurans from 3,3-disubstituted 1,2-allenyl perfluoroalkyl ketones. The perfluoroalkyl substituent and the amount of water in the solvent are important for the success of this electrophilic cyclization.     

Ruthenium-catalyzed reaction of alpha,beta-unsaturated imines with carbon monoxide and alkenes leading to beta,gamma-unsaturated gamma-butyrolactams: involvement of direct carbonylation at olefinic C[bond]H Bonds as a key step

The reaction of alpha,beta-unsaturated imines with CO and alkenes in the presence of Ru(3)(CO)(12) as a catalyst results in a three-component coupling reaction that gives alpha,alpha-disubstituted beta,gamma-unsaturated gamma-butyrolactams. The reaction proceeds via a two-step sequence involving the initial formation of ketone derivatives by catalytic carbonylation at the beta-olefinic C-H bonds of alpha,beta-unsaturated imines, followed by the (uncatalyzed) intramolecular nucleophilic attack of the imine nitrogen on the ketonic carbon to generate a tetrahedral intermediate, which then undergoes a 1,2-ethyl migration. The reaction of a cyclic unsaturated imine, derived from the reaction of (1R)-(-)-myrtenal with tert-butylamine, gives a beta-aminocyclopentene derivative, which is formed by an aldol-type condensation of the initially formed ketone, indicating the initial formation of ethyl ketone.     

Facile and regioselective synthesis of functionalized benzenes via cascade reactions of 1,2-allenic ketones with 4-sulfonyl crotonates

An efficient and regioselective synthesis of functionalized benzenes via the cascade reactions of 1,2-allenic ketones with 4-sulfonyl crotonates under mild reaction conditions has been established. Mechanistically, the formation of the title compounds involves a cascade procedure consisting of an intermolecular regioselective Michael addition followed by an intramolecular condensation and aromatization. Compared with those of α,β-unsaturated aldehydes/ketones, the reactions of 1,2-allenic ketones with 4-sulfonyl crotonates demonstrated contrary regio-selectivity and distinct reaction conditions. Moreover, the functionalized benzene products obtained herein were found to be ready intermediates for the synthesis of fluorenone and anthracenone derivatives.     

Ruthenium hydride-catalyzed addition of aldehydes to dienes leading to beta,gamma-unsaturated ketones

An efficient cross-addition reaction of dienes with aldehydes was developed by using RuHCl(CO)(PPh3)3 as a catalyst to give a wide variety of beta,gamma-unsaturated ketones, where a pi-allylruthenium species, derived from hydroruthenation of diene, may be involved as a key intermediate.     

Sc(OTf)3-catalyzed efficient synthesis of beta,beta-bis(indolyl) ketones by the double indolylation of acetic acid 2-methylene-3-oxobutyl ester

In the presence of 5 mol% Sc(OTf)3, double indolylation of acetic acid 2-methylene-3-oxo-butyl ester with differently substituted indoles readily afforded beta,beta-bis(indolyl) ketones. The reaction may proceed via a Sc(OTf)3-catalyzed SN2'-type substitution and subsequent conjugate addition.     

Synthesis of cyclopentenyl and cyclohexenyl ketones via [3 + 2] and [4 + 2] annulations of 1,2-allenic ketones简

In this paper, an efficient synthesis of cyclopentenyl ketones and cyclohexenyl ketones through tertiary phosphine catalyzed [3 ＋ 2] and [4 ＋ 2] annulations of 1,2-allenic ketones with activated alkenes has been developed. Compared with published synthetic methods on cyclopentenyl ketones and cyclohexenyl ketones, the protocols developed in this paper have the advantages such as readily available starting materials, mild reaction conditions and high efficiency.