Palladium‐catalyzed carbonylative cyclization of β‐bromo‐α,β‐unsaturated carboxylic acids with primary amines leading to N‐alkylmaleimides

Cyclic β‐bromo‐α,β‐unsaturated carboxylic acids are carbonylatively cyclized with primary amines under carbon monoxide pressure in MeCN in the presence of a catalytic amount of PdCl₂(PPh₃)₂ to give N‐alkylmaleimides. Copyright © 2012 John Wiley & Sons, Ltd.     

CuI/amino acid catalysis in coupling and cyclization of β‐bromo‐α,β‐unsaturated carboxylic acids with terminal alkynes leading to alkylidenefuranones

β‐Bromo‐α,β‐unsaturated carboxylic acids are coupled and cyclized with terminal alkynes in DMF at 110°C in the presence of a catalytic amount of CuI and amino acid along with a base to give alkylidenefuranones in good yields. Similar reaction under microwave irradiation also gave alkylidenefuranones in higher yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium‐catalyzed cyclization of β‐bromo‐α,β‐unsaturated ketones with arylhydrazines leading to 3‐substituted 1‐aryl‐1 H‐pyrazoles

β‐Bromo‐α,β‐unsaturated ketones are condensed with arylhydrazines to form hydrazones, which are in situ intramolecularly cyclized into 3‐substituted 1‐aryl‐1 H‐pyrazoles under a catalytic system of Pd(OAc)₂/1,3‐bis(diphenylhosphino)propane (dppp)/NaO^tBu. Copyright © 2012 John Wiley & Sons, Ltd.     

Palladium‐catalyzed decarboxylative coupling of α,β‐unsaturated carboxylic acids with aryl tosylates

We report a general method for selective cross‐coupling of α,β‐unsaturated carboxylic acids with aryl tosylates enabled by versatile Pd(II) complexes. This method features the general cross‐coupling of ubiquitous α,β‐unsaturated carboxylic acids by decarboxylation. The transformation is characterized by its operational simplicity, the use of inexpensive, air‐stable Pd(II) catalysts, scalability and wide substrate scope. The reaction proceeds with high trans selectivity to furnish valuable (E)‐1,2‐diarylethenes.     

Ligand‐free CuI‐catalyzed coupling and cyclization of β‐bromo‐α,β‐unsaturated amides with formamide leading to pyrimidinones

β‐Bromo‐α,β‐unsaturated amides were coupled and cyclized with formamide in DMF at 100°C in the presence of a catalytic amount of a copper(I) salt along with a base to give the corresponding pyrimidinones in good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

CuI/amino acid‐catalyzed coupling and cyclization of β‐bromo‐α,β‐unsaturated amides with terminal alkynes leading to (3Z)‐3‐alkylidenepyrrol‐1‐ones

β‐Bromo‐α,β‐unsaturated amides are coupled and cyclized with terminal alkynes in DMF at 110 °C in the presence of a catalytic amount of CuI and amino acid along with a base to give the corresponding (3Z)‐3‐alkylidenepyrrol‐1‐ones in moderate to good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium‐catalyzed carbonylative cyclization of 1‐bromoallyl bromides with anilines leading to 1‐aryl‐1H‐pyrrol‐2(5H)‐ones

1‐Bromoallyl bromides are carbonylatively cyclized with anilines under carbon monoxide pressure in DMF in the presence of a catalytic amount of a palladium catalyst along with a base to give the corresponding 1‐aryl‐1H‐pyrrol‐2(5H)‐ones in moderate to good yield. Copyright © 2012 John Wiley & Sons, Ltd.     

Palladium‐catalyzed three‐component cyclization of 2‐bromocyclohex‐1‐enecarboxylic acids with carbon monoxide and arylhydrazines leading to 2‐anilinohydroisoindoline‐1,3‐diones

2‐Bromocyclohex‐1‐enecarboxylic acids are carbonylatively cyclized with arylhydrazines or their hydrochlorides in tetrahydrofuran at 120 °C under carbon monoxide pressure in the presence of a catalytic amount of PdCl₂ and 1,3‐bis(diphenylphosphino)propane along with Et₃N to give 2‐anilinohydroisoindoline‐1,3‐diones. Copyright © 2015 John Wiley & Sons, Ltd.     

Palladium‐catalyzed carbonylative cyclization of 3‐bromoallyl alcohols leading to furan‐2(5H)‐ones

3‐Bromoallyl alcohols are carbonylatively cyclized under carbon monoxide pressure in toluene in the presence of a catalytic amount of Pd(OAc)₂ and PPh₃ along with Na₂CO₃ to give furan‐2(5H)‐ones in good yields. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of β,γ‐Unsaturated Acids from Allenes and Carbon Dioxide

Hidden talent : Often perceived to be too thermodynamically and kinetically inert to be a useful chemical feedstock, carbon dioxide adds to allenes under exceptionally mild reductive conditions in the presence of a palladium pincer complex to give β,γ‐unsaturated carboxylic acids (see scheme). This transformation is discussed in the context of the requirements for CO₂ fixation. DMF=N,N‐dimethylformamide, Tf=trifluoromethanesulfonyl.

     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

NH2SO3H–SiO2 as a new water‐compatible,recyclable heterogeneous catalyst for the synthesis of novel (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction

NH₂SO₃H–SiO₂/water as a novel catalytic system was used for the synthesis of (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction at reflux conditions. The methodology was of general applicability and the catalyst exhibited activity up to five cycles. The catalyst was characterized for the first time using FT‐IR, X‐ray diffraction and scanning electron microscopic–energy dispersion analytical X‐ray. The stability of the catalyst was evaluated by differential scanning calorimetry and TGA/differential thermal analysis. High efficiency of the catalyst along with its recycling ability and the rather low loading demonstrated in reactions are the merits of the presented protocol. Copyright © 2013 John Wiley & Sons, Ltd.     

Photolysis of α,β‐Epoxyketones: A Green Synthesis of β‐Hydroxyenones through Tandem H‐Abstraction,Ring Cleavage and Isomerisation

The photochemical behavior of various substituted epoxycarbonyl compounds consisting of more than one possible photo‐labile site (i.e. δ‐hydrogen, β‐hydrogen and epoxide ring) has been investigated. These compounds on photo‐irradiation produced the β‐hydroxyenones in an eco‐friendly green approach. Mechanistically, these photo‐transformations have been envisaged to occur via an intramolecular β‐hydrogen abstraction by the carbonyl group of benzoyl moiety to generate the 1,3‐biradical followed by epoxide ring opening that isomerizes into the photoproducts. The photolysis of the probed epoxy ketones didn’t furnish any photoproduct through δ‐hydrogen abstraction, whatsoever. This exclusive preference for β‐H abstraction over δ‐H abstraction by carbonyl group has been vindicated by the MM2 energy mini‐ mized program for the investigated photochemical substrates. The structures of these photoproducts were established from the analysis of their spectral parameters (IR, ¹H/¹³C NMR and Mass) and single crystal X‐ray crystallography data.     

Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams

The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M⁺‐29], [M⁺‐55], and [M⁺‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.     

Reaction of α,β‐unsaturated ketones with cerium(IV) salts in alcohol

Reaction of α,β‐unsaturated ketones with cerium(IV) salts or lanthanide triflates in alcohols gave good yields of the corresponding β‐alkoxy compounds. In the case of 2‐cyclopentenone and 2‐cyclohexenone, the 1,1,3‐trialkoxy acetal derivatives were obtained preferentially accompanied by β‐alkoxyketone, except 2‐cycloheptenone. However, in the reaction of 2‐cycloheptenone with alcohol using cerium(IV) sulfate (CS)‐molecular sieve, 1,1,3‐trialkoxy derivatives were obtained. Also, in the cases of 1‐penten‐3‐one, 4‐hexen‐3‐one and 3‐hepten‐2‐one, 1,1,3‐trialkoxy derivatives were obtained preferentially. Copyright © 2006 John Wiley & Sons, Ltd.     

Palladium‐Catalyzed Carbonylative α‐Arylation to β‐Ketonitriles

A carbonylative α‐arylation process employing unactivated nitriles for the first time is described. The reaction tolerates a range of (hetero)aryl iodides and several nitrile coupling partners. No prefunctionalization of the nitriles is necessary and the resulting β‐ketonitriles are obtained in good to excellent yields. The methodology also allows for a convenient ¹³C‐labelling of the generated carbonyl moiety.     

Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters

Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by ¹H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597