Aza-Baylis-Hillman reaction of salicyl N-tosylimines with methyl vinyl ketone, ethyl vinyl ketone or phenyl vinyl ketone

Reactions of salicyl N-tosylimines with methyl vinyl ketone, ethyl vinyl ketone or phenyl vinyl ketone proceeded smoothly under mild conditions to give the corresponding chromanes or aza-Baylis-Hillman adducts in moderate to excellent yields in the presence of phosphine or nitrogen Lewis base.     

Bifunctional chiral phosphine-containing Lewis base catalyzed asymmetric Morita–Baylis–Hillman reaction of aldehydes with activated alkenes

A series of novel bifunctional chiral phosphine-containing Lewis bases were synthesized and successfully applied to the asymmetric Morita–Baylis–Hillman reaction of aldehydes with methyl vinyl ketone (MVK) and ethyl vinyl ketone (EVK) to give the corresponding adducts in moderate yields and enantioselectivities under mild reaction conditions.     

Traditional Morita-Baylis-Hillman reaction of aldehydes with methyl vinyl ketone co-catalyzed by triphenylphosphine and nitrophenol

In the Morita-Baylis-Hillman reaction of aldehydes with methyl vinyl ketone (MVK), we found that in the presence of a catalytic amount of phenol, the Lewis base triphenylphosphine can effectively promote the reaction to give the corresponding normal Morita-Baylis-Hillman adducts in good yields. The mechanism has been investigated by 31P NMR spectroscopy. The solvent and substituent effects were also examined.     

Reaction of α,β-unsaturated trifluoromethyl ketones with ethyl cyanoacetate

β-Aryl-substituted α,β-unsaturated trifluoromethyl ketones react with ethyl cyanoacetate to give the corresponding Michael addition products, ethyl 3-aryl-2-cyano-6,6,6-trifluoro-5-oxohexanoates, which are formed as mixtures of two diastereoisomers. The reaction time and product yield depend on electron-donating properties of the substituent in the initial ketone. The reaction is not accompanied by intramolecular cyclization of the Michael adducts.     

The cross-aldol reaction of hexafluoroacetone (HFA) with ketones catalyzed by an acid

The cross-aldol reactions of hexafluoroacetone (HFA) and ketones using an acid catalyst are reported. When concentrated sulfuric acid was employed as the catalyst, HFA reacted regioselectively with various ketones at 50-100 °C to give the aldol adducts (6) in good yields. The reaction is initiated by an acid-catalyzed transformation of the ketone into the corresponding enol that reacts with HFA. The obtained adducts (6) can be reduced with hydrogen under a Ru/C catalyst to lead to the corresponding fluorine-containing diols (13).     

Aza-Morita–Baylis–Hillman reaction with ion-supported Ph3P

Various N-tosyl arylimines reacted with methyl vinyl ketone and ethyl vinyl ketone in the presence of ion-supported Ph₃P A and B to give adducts, N-(2′-methylene-3′-oxo-1′-arylbutyl)-4-methylbenzenesulfonamides and N-(2′-methylene-3′-oxo-1′-arylpentyl)-4-methylbenzenesulfonamides, respectively, in good yields with high purity by simple diethyl ether extraction of the reaction mixture. Moreover, ion-supported Ph₃P A and B could be repeatedly used for the same reaction to provide the corresponding adducts while maintaining good yields with high purity.     

Catalytic asymmetric Michael reactions using a chiral rhodium complex

Catalytic asymmetric Michael reaction of β-keto esters and methyl vinyl ketone was achieved using a chiral diamine-based Rh complex to give the Michael adducts in up to 75% e.e.     

Enantioselective Michael addition of beta-keto esters to methyl vinyl ketone employing a chiral N,N'-dioxide-scandium trifluoromethanesulfonate complex as a catalyst

An enantioselective Michael addition of beta-keto esters to methyl vinyl ketone exploiting a chiral N,N'-dioxide-scandium trifluoromethanesulfonate complex as a catalyst affords the corresponding Michael adducts in high yields and with enantioselectivities of up to 80% ee.     

Aza-Morita-Baylis-Hillman reaction of ethyl (arylimino)acetate with methyl vinyl ketone and ethyl vinyl ketone

Aza-Morita-Baylis-Hillman (aza-MBH) reaction of ethyl (arylimino)acetate with methyl vinyl ketone and ethyl vinyl ketone has been investigated. We found that aza-MBH adducts 1 could be formed in the presence of DABCO (30 mol %) and the corresponding adducts 2 could be obtained in the presence of PPh₃ (30 mol %) in moderate to good yields in acetonitrile under mild conditions, respectively.     

Catalytic, asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines with activated olefins by quinidine-derived chiral amines

The chiral nitrogen Lewis base, tricyclic cinchona alkaloid derivative TQO, is an effective promoter in the catalytic, asymmetric aza‐Baylis–Hillman reaction of N‐sulfonated imines Ar? CH?NR′ 1 (R′ = Ts, Ms, Ns, SES) with various activated olefins such as methyl vinyl ketone (MVK), ethyl vinyl ketone (EVK), acrolein, methyl acrylate, phenyl acrylate, or α‐naphthyl acrylate to give the corresponding adducts in moderate to good yields with good to high ee (up to 99 %) at ?30 °C or 45 °C in various solvents, including DMF/MeCN (1:1, v/v). The first such reaction of 1 with the simplest Michael acceptor MVK and methyl acrylate has been achieved with excellent enantioselectivity. The adducts derived from MVK and EVK had the opposite absolute configuration to those from acrolein, methyl acrylate, phenyl acrylate, and α‐naphthyl acrylate. A plausible mechanism has been proposed on the basis of previous reports and the authors’ investigations. An effective bifunctional chiral nitrogen Lewis base–Brønsted acid system has been revealed in this type of aza‐Baylis–Hillman reaction.     

手性含硫恶唑硼烷催化芳酮不对称还原反应的量子化学研究

用HF方法在6-31G^*基组下,对手性含硫恶唑硼烷催化苯乙酮不对称还原反应进行了量子化学从头算研究。还原反应经历了催化剂-硼烷加合物、催化剂-硼烷-酮加合物、催化剂-烷氧基硼烷加合物的生成以及催化剂-烷氧基硼烷加合物的离解过程。催化剂-硼烷加合物、催化剂-硼烷-酮加合物和催化剂-烷氧基硼烷加合物的生成分别为放热、吸热、放热过程;催化剂-烷氧基硼烷加合物离解成催化剂烷氧基硼烷为吸热过程。催化剂-硼烷-酮加合物和催化剂-烷氧基硼烷加合物都存在四种稳定的结构。最有利于氢转移的催化剂-硼烷-酮加合物结构是次低能量结构,并且具有扭曲的船形结构。催化剂-烷氧基硼烷加合物含有一个B-O-B-N四元环,尽管四元环有较大的张力,但加合物仍有较高的稳定性。     

Direct Synthesis of β-Alkyl N-Aryl Aza Baylis-Hillman Adducts via Nitroso-Ene Reaction

A new approach for the direct Fe-catalyzed synthesis of β-alkyl N-aryl aza Baylis-Hillman (ABH) adducts is reported. This approach involves the formation of a C-N bond via a nitroso-ene reaction. This is a simple, fast, and best alternate method to overcome the substrate scope limitations of the ABH reaction, which converts allyl esters and carbonyl compounds to novel ABH adducts. A variety of arylhydroxylamines reacted with esters, aldehydes, ketone, and nitriles to yield the corresponding products in moderate to excellent yields.     

Reaction of Substituted Cyclopentadienyl-magnesium-Chloride with Carbonyl Compound ( Ⅰ )——Reaction of (1, 1-Dialkyl-3-Butenyl) Cyclopentadienyl-magnesium-chloride with Ketones

The substituted cyclopentadienyl-magnesium-chloride, obtained by exocyclic addition of 6,6-dialkylfulvene and allyl-magnesium-chloride, reacted with the ketone 3, the product was hydrolyzed and dehydrated to give the 2-(1 ,1-dialkyl-3-butenyl)-6,6-dialkyl-fulvene 5. The structure of 5 was determined by using the 1H NMR spectra of 5 and the adducts of 5 with tetracyanoethylene.     

1,4-Conjugate addition of 2-hydroxynaphthazarins to acyclic and cyclic α,β-unsaturated ketones. Prototropic ring-chain tautomerism of the adducts

TsOH-Catalyzed reactions of 6,7-disubstituted 2-hydroxynaphthazarins and acyclic or cyclic α,β-enones afforded the corresponding Michael-type adducts, viz., 3-substituted naphthazarins in 17–78% yields. ¹H and ¹³C NMR and IR spectroscopy showed that the adducts with cyclohexenone and methyl vinyl ketone exist in CDCl₃ solutions as mixtures of open-chain and cyclic tautomers, whereas the adducts with cyclopentenones exist only as the open-chain forms.     

Stereoselective synthesis of syn-α-methyl-β-hydroxy esters

Boron enolates of an ethyl ketone structurally related to erythrulose react with achiral aldehydes in a highly stereoselective fashion to yield 1,2-syn/1,3-syn stereoisomers. Oxidative cleavage of the aldol adducts yields enantiopure O-formylated syn-α-methyl-β-hydroxy esters, easily cleaved to the corresponding hydroxyl-free compounds. The aforementioned ketone behaves therefore as a chiral propionate enolate equivalent.     

An efficient synthesis of ferrocenyl substituted 1,5-diketone and cyclic α,β-unsaturated ketones under ultrasound irradiation

Michael reactions of deoxybenzoin or dibenzyl ketone with ferrocenyl substituted chalcones catalyzed by sodium hydroxide under ultrasound irradiation can afford the corresponding Michael adducts with excellent yields. It presents a convenient, efficient and simple method for the preparation of ferrocenyl substituted 1,5-diketone compounds in the presence of ultrasound irradiation. In addition, the formation of cyclic, α,β-unsaturated ketones via the reactions of dibenzyl ketone with ferrocenyl substituted chalcones were found, and characterized by X-ray crystal structure analysis.     

Enantioselective Michael addition of 3-aryl-substituted oxindoles to methyl vinyl ketone catalyzed by a binaphthyl-modified bifunctional organocatalyst

The enantioselective conjugate addition reaction of 3-aryl-substituted oxindoles with methyl vinyl ketone promoted by binaphthyl-modified bifunctional organocatalysts was investigated. The corresponding Michael adducts, containing a quaternary center at the C3-position of the oxindoles, were generally obtained in high yields with excellent enantioselectivities (up to 91% ee).     

A Novel Reactivity of Phosphanylalumane (>P−Al<): Reversible Addition of a Saturated Interelement Bond to Olefins

The reversible addition of olefins to a phosphanylalumane, P−Al single-bond species, was investigated. The P−Al bond added to ethylene and relatively small terminal alkenes (propylene and hex-1-ene) at room temperature to give the corresponding alkene adducts. Heating the terminal alkene adducts released the corresponding alkenes and regenerated the P−Al bond, but no release of ethylene was observed even under vacuum conditions. The reactivity of ethylene adduct as a new saturated C₂ vicinal P/Al-based FLP was also investigated. The ethylene adduct was found to undergo complexation with nitriles to give the corresponding nitrile adducts to the Al center, which retained the ethylene tether as in the case of the corresponding P/B-based FLP. However, the reactivity of ethylene toward CO₂ and benzaldehyde differed from that of the P/B system giving the corresponding adducts.     

Synthesis of dihydrothieno[2,3‐b]pyridines based on titanium(IV) chloride‐mediated michael reactions of 2‐amino‐4,5‐dihydro‐3‐thiophenecarbonitriles with α,β‐unsaturated ketones

2‐Arnino‐4,5‐dihydro‐3‐thiophenecarbonitriles 1a‐c reacted with α,β‐unsaturated ketones (e.g. methyl vinyl ketone 2 and benzalacetone 3 ) in the presence of titanium(IV) chloride to give the corresponding Michael adducts 4a‐c and 5a‐c. Thermal treatment of compounds 4a‐c and 5a‐c with titanium(IV) chloride caused intramolecular cyclocondensation to yield the corresponding tetrahydrothieno[2,3‐b]pyridines 6a‐c and 7a‐c. Aromatization of 6a‐c and 7a‐c with potassium tert‐butoxide in refluxing tert‐butyl alcohol pro ceeded smoothly to afford the corresponding dihydrothieno[2,3‐b]pyridines 8a‐c and 9a‐c.     

Alpha'-hydroxy enones as achiral templates for Lewis acid-catalyzed enantioselective Diels-Alder reactions

alpha'-Hydroxy enones react with dienes in the presence of (S,S)-[Cu(tBu-box)](OTf)2 or (S,S)-[Cu(tBu-box)](SbF6)2 (2 to 10 mol %) to afford the corresponding Diels-Alder adducts in high yield and selectivity. Isomeric ratios (regioselectivity, endo/exo or cis/trans) of up to >99:1 and ee values of up to >99% are obtained. Significantly, difficult dienes such as isoprene, 2,3-dimethyl butadiene and piperylene behave satisfactorily. Subsequent oxidative cleavage of the ketol in the resulting cycloadducts by treatment with cerium ammonium nitrate (CAN) yields the corresponding enantiopure carboxylic acids. Alternatively, carbonyl addition and subsequent diol cleavage with CAN produces the corresponding ketone adducts.