Regioselective addition of thiophenol to α,β-unsaturated N-acylbenzotriazoles

Regioselective addition of thiophenol to α,β-unsaturated N-acylbenzotriazoles has been achieved by controlling the conditions. Thus, three types of products, namely α,β-unsaturated thioesters, β-thiophenoxy substituted N-acylbenzotriazoles, and β-thiophenoxy substituted thioesters were selectively obtained in good to excellent yields.     

Synthesis of polycyclic indolizine derivatives via one-pot tandem reactions of N-ylides with dichloro substituted α,β-unsaturated carbonyl compounds

Convenient and regioselective syntheses of 1,2-annulated, and 1,2-, 5,6- and 1,2-, 7,8-bisannulated polycyclic indolizine derivatives have been achieved by one-pot tandem reactions of cyclic N-ylides derived from the corresponding N-substituted pyridinium, quinolinium, and isoquinolinium salts 1-3 with dichloro substituted α,β-unsaturated carbonyl compounds 4-7. The reactions of the N-ylides with 2,3-dichloroindenone 4, 3,4-dichlorocoumarin 5, and 4a,6,7,8a-tetrachloro-1,4-methanonaphthalene-5,8-dione 6 proceed by sequential [3+2] cycloaddition and elimination of hydrogen chlorides from the cycloadducts. On the other hand, reactions of the N-ylides with 2,3-dichloro-1,4-naphthoquinone 7 take place via a novel reaction sequence to give the products 15-17.     

Alkylating potential of α,β-unsaturated compounds

Alkylation reactions of the nucleoside guanosine (Guo) by the α,β-unsaturated compounds (α,β-UC) acrylonitrile (AN), acrylamide (AM), acrylic acid (AA) and acrolein (AC), which can act as alkylating agents of DNA, were investigated kinetically. The following conclusions were drawn: i) The Guo alkylation mechanism by AC is different from those brought about the other α,β-UC; ii) for the first three, the following sequence of alkylating potential was found: AN > AM > AA; iii) A correlation between the chemical reactivity (alkylation rate constants) of AN, AM, and AA and their capacity to form adducts with biomarkers was found. iv) Guo alkylation reactions for AN and AM occur through Michael addition mechanisms, reversible in the first case, and irreversible in the second. The equilibrium constant for the formation of the Guo-AN adduct is K(eq) (37 °C) = 5 × 10(-4); v) The low energy barrier (≈10 kJ mol(-1)) to reverse the Guo alkylation by AN reflects the easy reversibility of this reaction and its possible correction by repair mechanisms; vi) No reaction was observed for AN, AM, and AA at pH < 8.0. In contrast, Guo alkylation by AC was observed under cellular pH conditions. The reaction rate constants for the formation of the α-OH-Guo adduct (the most genotoxic isomer), is 1.5-fold faster than that of γ-OH-Guo. vii) a correlation between the chemical reactivity of α,β-UC (alkylation rate constants) and mutagenicity was found.     

Regioselective synthesis of α-bromo-α,β-unsaturated carbonyl compounds via photocatalytic α-bromination reactions

A visible light-mediated approach for the preparation of α-bromo-α,β-unsaturated ketones and aldehydes was developed. In comparison to traditional methods that generally take two steps to afford the above compounds, this protocol was highlighted by its operational simplicity, avoiding using hazardous bromine and mild reaction conditions.     

Copper-catalyzed β-boration of α,β-unsaturated carbonyl compounds with tetrahydroxydiborane

The copper-catalyzed β-boration of α,β-unsaturated carbonyl compounds with tetrahydroxydiborane has been developed. This diboron reagent allows direct, efficient access to boronic acids and their derivatives. Primary, secondary, and tertiary α,β-unsaturated amides are converted to the corresponding β-trifluoroboratoamides in good to excellent yields. The β-boration of a variety of α,β-unsaturated esters and ketones is also reported.     

Formation of fluorosulfatodimerization products in reactions of perfluoroaliphatic α,β-unsaturated carbonyl compounds and conjugated dienes with electrochemically generated peroxydisulfuryldifluoride

Reactions of fluoroaliphatic α,β-unsaturated carbonyl compounds and perfluoro-2,7-dimethylocta-3,5-diene with electrochemically generated peroxydisulfuryldifluoride proceed to give both 1∶1 adducts and fluorosulfatodimerization products, whose formation is explained by generation of heteroallyl and allyl radicals due to the addition of a fluorosulfonyloxy radical to the sterically hindered vinyl carbon atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2207–2209, November, 1999.     

Selective carbometallation of α,β-unsaturated carbonyl compounds and substituted oxacyclopropanes with zirconium-diene complexes

The reactions of zirconium-dience complexes, ZrCp₂(s-cis-diene), with bifunctional electrophiles, i.e. α,β-unsaturated ketones, unsaturated esters and substituted oxacyclopropanes, were investigated. Reaction of ZrCp₂(s-cis-isoprene) with an equivalent of 3-buten-2-one or alkyl acrylates, selectively gives 1,2-addition products. CC bond formation occured at the C(1) atom of the isoprene moiety whereas 1,3-pentadiene-, 2-methyl-1,3-pentadiene- and 2,4-dimethyl-1,3-pentadiene complexes induced the regioselective 1,2-addition at the C(4) position of the diene moiety. Phenyloxacyclopropane and 2-methyl-3-phenyl-oxacyclopropane also react with ZrCp₂(isoprene) leading to CC bond formation from the C(1) atom of isoprene to the oxirane carbon bearing the phenyl group. The corresponding reactions of 2-methyl-2-butene-1,4-diylmagnesium with α,β-unsaturated carbonyl compounds were also studied and found to give quite different products.     

CuCl/bipyridine-catalyzed addition reactions of arylboroxines with aldehydes, α,β-unsaturated ketones, and N-tosyl aldimines

CuCl/bipyridine-catalyzed addition reactions of arylboroxines with aldehydes and α,β-unsaturated ketones at elevated temperatures were described. By using the microwave energy, CuCl/bipyridine-catalyzed addition reactions of arylboroxines with aldimines were also realized.     

Organocatalytic enantioselective Michael addition reactions of fluoromalonates with α,β-unsaturated aldehydes

A new organocatalytic enantioselective Michael addition of α-fluoromalonate to enals has been developed.The process is efficiently catalyzed by readily available chiral diphenylpyrolinol TES ether under mild reaction conditions to afford versatile highly enantioenriched fluorinated aldehydes.     

Palladium-catalyzed desulfitative addition of sodium sulfinates with α,β-unsaturated carbonyl compounds

A palladium-catalyzed desulfitative conjugate addition of sodium sulfinates with α,β-unsaturated carbonyl compounds is described. The reaction showed very good selectivity and tolerated a wide range of functionalities under an atmosphere of argon.     

Highly diastereo- and enantioselective one-pot Michael-Aldol reactions of α,β-unsaturated aldehydes with imidazole derivatives

Highly diastereo- and enantioselective one-pot Michael-Aldol reactions of α,β-unsaturated aldehydes with imidazole derivatives have been developed. The cascade reactions products could be obtained with three stereocenters in high yields and excellent diastereo- and enantioselectivities.     

Copper-mediated synthesis of α-trifluoromethylthio- and seleno-α,β-unsaturated carbonyl compounds

A novel route to the synthesis of α-trifluoromethylthio- and seleno-α,β-unsaturated carbonyl compounds via a copper-mediated trifluoromethylthiolation/trifluoromethylselenolation of α-halo-α,β-unsaturated carbonyl substrates is reported.     

Cinchona-based primary amine-catalyzed enantioselective aza-Michael reactions of pyrroles with α,β-unsaturated aldehydes

The cinchona-based primary amine-catalyzed enantioselective aza-Michael reaction of α,β-unsaturated aldehydes with 4,5-dihalo-1H-pyrrole-2-carbonitriles as the N-centered heteroaromatic nucleophile, followed by chemoselective reduction provided the corresponding chiral aza-Michael products in good yields and with excellent enantioselectivities (90–97% ee).     

A modular approach to α,β-unsaturated N-aryl ketonitrones

A modular approach to α,β-unsaturated N-aryl ketonitrones has been developed. Specifically, condensation of anilines and enals followed by alkylation of the resulting α,β-unsaturated imines provided N-allyl anilines, which were subjected to oxidation with Oxone® to form α,β-unsaturated N-aryl ketonitrones. This modular approach is general and provides rapid access to diversely substituted α,β-unsaturated N-aryl ketonitrones with a single purification step in good yields.     

Preparation of silyl-protected γ-hydroxylated α,β-unsaturated acetylenic ketones and their reactions with some nucleophiles

A number of 5-siloxylated 1,1-diethoxy-3-alkyn-2-ones were prepared from the corresponding ketals. The t-butyldiphenylsiloxy derivatives were stable, whereas the trimethylsilyl analogs were unstable. The former compounds were reacted with diethylamine, lithium dimethylcuprate, and 1,3-propanedithiol and gave Michael adducts in good to very good yields. The amine and cuprate gave the conjugated alkenones, the former in a stereospecific manner (Z), the latter stereospecifically (E) in one case but otherwise stereoselectively with an E preponderance. With the dithiol bisaddition occurred, and the corresponding 1,3-dithiane was obtained in excellent yield. Attempts to make 1,3-dithianes from 1,3-propanedithiol and 1,1-diethoxy-4-diethylaminoalk-3-en-2-ones failed.     

Preparation of novel multifunctional amino alcohols from nitroparaffins and α,β-unsaturated aldehydes

A series of novel multifunctional amino alcohols were prepared by tandem Michael–Henry reaction by reacting nitroalkanes such as 2-nitropropane with readily available α,β-unsaturated aldehydes. The dinitro compounds were further reduced by catalytic hydrogenation to obtain respective diamines. This synthetic route provides a very convenient method of preparing multifunctional amino alcohols.     

1,4-Addition of tetraethyl fluoromethylenebisphosphonate to α,β-unsaturated compounds

Tetraethyl fluoromethylenebisphosphonate in the presence of cesium carbonate in DMF undergoes efficient 1,4-addition to Michael acceptors having terminal double bond such as α,β-unsaturated ketones, esters, sulfones, sulfoxides, and phosphonates to yield the corresponding adducts (α-alkyl-α-fluoromethylenebisphosphonates) in good to excellent yields.     

Palladium catalyzed reactions of α-bromo-α,β-unsaturated carbonyl compounds with 1-(E)-alkenylboronic acids

A new synthesis of functionalized 1,3-dienes is described based on the palladium catalyzed coupling reaction of 1-(E)-alkenylboronic acids with α-bromo-α,β-unsaturated carbonyl compounds.     

Chiral tertiary amine N-oxides in asymmetric epoxidation of α,β-unsaturated ketones

Chiral tertiary amine N-oxides have been shown to undergo stereoselective oxygen transfer reaction in the epoxidation of chalcone derivatives with modest to good enantioselectivity.