Simple and New Protocol for the Synthesis of Novel (z)-3-Arylidenebenzothiazepin-4-ones Using Baylis–Hillman Derivatives

A simple synthesis of novel (Z)-3-arylidene-2,3-dihydrobenzo[b][1,4]thiazepin-4(5H)-ones from bromo compounds derived from Baylis–Hillman adducts involving selective S-alkylation followed by a lactum formation has been described.     

A new application of Baylis–Hillman alcohols to a diastereoselective synthesis of 3-nitrothietanes

Three key reactions, the generation of a nucleophile, an thia-Michael addition and an intramolecular cyclisation, were used to achieve an efficient one-pot diastereoseletive synthesis of 3-nitrothietanes. Thus, Baylis–Hillman alcohols and their aldehydes were reacted with either O,O-diethyl hydrogen phosphorodithioate or O,O-diethyl hydrogen phosphorodithioate in combination with a task-specific ionic liquid [bmim]X–Y to afford the corresponding 2,3-di- or 2,3,4-trisubstituted thietanes, respectively. The reaction is high yielding and proceeds with complete diastereoselectivity in favour of the trans isomers.     

Lipase-catalyzed kinetic resolution of Baylis–Hillman products

Lipase-catalyzed kinetic resolution of the various Baylis–Hillman products, α-methylene-β-hydroxy compounds, were examined. When lipase PS was used as a biocatalyst in acetonitrile, transesterification of racemic ethyl 3-hydroxy-2-methylenebutanoate or 3-hydroxy-2-methylenepentanoate proceeded in a practical enantiomeric excess. The resolution by hydrolysis of the acetate derivatives was also tried. In contrast, in case of racemic ethyl 3-acetoxy-2-methylenepentanoate, under the conditions using lipase AK, the E value of the resolution was >321.     

Asymmetric Morita–Baylis–Hillman reaction of chiral glyoxylates

The first Morita–Baylis–Hillman reaction of chiral glyoxylic acid derivatives, i.e. N-glyoxyloyl-(2R)-bornane-10,2-sultam and (−)-8-phenylmenthyl glyoxylate is described. The reaction with cyclic α,β-unsaturated ketones proceeded under the catalytic influence of dimethyl sulfide in the presence of titanium tetrachloride. The adducts were obtained with very high diastereoisomeric excess (over 95% d.e.) and typical yields of 78%. The absolute configuration of the newly created stereogenic center was established by X-ray crystallographic analysis.     

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.     

Facile synthesis of bisphosphine monoxides from Morita–Baylis–Hillman carbonates

A facile two-step synthesis of bisphosphine monoxides (BPMOs, with both the phosphine and phosphine oxide moieties within one molecule) from readily available Morita–Baylis–Hillman (MBH) carbonates was realized. Under the catalysis of DABCO, the MBH carbonates undergo allylic phosphorylation reaction with diphenylphosphine oxide or diethyl phosphonate to give monophosphine oxides bearing an activated alkene moiety; subsequent base-catalyzed hydrophosphination of the prepared monophosphine oxide with HPPh₂ readily affords the BPMOs.     

Novel Synthesis of (E)-3-Arylidene-2,3-dihydrobenzo[b][1,4]oxazepin-4(5H)-ones Using Baylis–Hillman Derivatives via Reductive Cyclization

A simple synthesis of novel (E)-3-arylidene-2,3-dihydrobenzo[b][1,4]oxazepin-4(5H)-ones from bromides of the Baylis--Hillman adducts using Fe/AcOH for the in situ reduction of nitro group, into an amino group, followed by the cyclization as a key step, has been described.     

Synthesis of Novel Poly(ethyleneglycol)-400 Ionic Liquid and Its Application in Morita–Baylis–Hillman Reaction

Novel Poly(ethyleneglycol)-400 ionic liquid containing imidazolium cations have been synthesized by the atom-efficient reaction of 1,2-dimethylimidazole with p-toluenesulfonate; the p-toluenesulfonate provides the anionic component of the resultant ionic liquid. It have been used for the first time as a new solvent for the Morita–Baylis–Hillman reaction under ambient conditions. A wide variety of aldehydes and active olefins participate very efficiently, resulting in good to excellent yields of products.      

Asymmetric synthesis of homochiral Baylis–Hillman products employing (R)-N-methyl-N-α-methylbenzyl amide

The conjugate addition of (R)-N-methyl-N-α-methylbenzyl amide to tert-butyl cinnamate followed by an asymmetric aldol reaction and subsequent N-oxidation/Cope elimination affords β-substituted homochiral Baylis–Hillman products in good yield.     

Simple and Advantageneous Stereoselective Synthesis of (Z)-Allyl Phosphonates Starting from Baylis–Hillman Adducts

Baylis–Hillman adducts 3-hydroxyl-2-methylene alkanoates have been converted in one pot into the corresponding (Z)-allyl phosphonates by treatment with FeCl₃ and trialkyl phosphites in toluene under reflux. The products are formed in excellent yields (88–98%) within 1–1.5 h. The process is highly convenient and efficient, cost-effective, and remarkably stereoselective.     

Solvent-dependent Baylis–Hillman reactions for the synthesis of 3-benzyl-3-hydroxyoxindoles and benzo-δ-sultams

We have developed a solvent-dependent method for the preparation of novel benzo-δ-sultam and 3-benzyl-3-hydroxy-N-methyloxindole scaffolds. A variety of 3-(methoxy(phenyl)methyl)-1-methyl-1H-benzo-[c][1,2]thiazine 2,2-dioxides and 3-benzyl-3-hydroxy-1-methylindolin-2-ones were obtained in moderate to high yields via DBU-catalyzed Baylis–Hillman reaction of a number of (E)-N-(2-formylphenyl)-N-methyl-2-phenylethenesulfonamides in DMF and MeOH, respectively. The proof of the structures relies on analytical investigation and X-ray crystallography. Whereas reaction of (E)-N-(2-formylphenyl)-N-methyl-2-phenylethenesulfonamides in MeOH presumably proceeds through intramolecular Baylis–Hillman/dehydration, 3-hydroxy-N-methyloxindoles seem to have been generated via intramolecular Baylis–Hillman/1,3-H shift/oxidation/intramolecular cyclization tandem sequences in DMF.     

Et3B-mediated palladium-catalyzed direct allylic substitution reactions of Morita–Baylis–Hillman alcohols with aromatic amines

An efficient, direct allylic amination of both cyclic and acyclic Morita–Baylis–Hillman alcohols with aromatic amines, in tetrahydrofuran (THF) at room temperature, catalyzed by Pd(0)/Et₃B, is reported herein. The corresponding amines are obtained with a high α -regioselectivity in 65–87% yields.     

Synthesis of fused pyrimidone derivatives of 4-pyrones from the acetates of Baylis–Hillman adducts

A series of fused pyrimidone derivatives of 4-pyrones was synthesized by conversion of the acetates of Baylis−Hillman adducts obtained from 2-formyl-4-pyrones with 2-aminopyridine and 2-aminothiazole.     

Direct Umpolung Morita–Baylis–Hillman like α-Functionalization of Enones via Enolonium Species

Herein we report on the umpolung of Morita–Baylis–Hillman type intermediates and application to the α-functionalization of enone C−H bonds. This reaction gives direct access to α-chloro-enones, 1,2-diketones and α-tosyloxy-enones. The latter are important intermediates for cross-coupling reaction and, to the best of our knowledge, cannot be made in a single step from enones in any other way. The proposed mechanism is supported by spectroscopic studies. The key initial step involves conjugate attack of an amine (DABCO or pyridine), likely assisted by hypervalent iodine acting as a Lewis acid leading to formation of an electrophilic β-ammonium-enolonium species. Nucleophilic attack by acetate, tosylate, or chloride anion is followed by base induced elimination of the ammonium species to give the noted products. Hydrolysis of α-acetoxy-enones lead to formation of 1,2-diketones. The α-tosyl-enones participate in Negishi coupling reactions under standard conditions.     

Construction of polycyclic spirooxindoles through [3+2] annulations of Morita–Baylis–Hillman carbonates and 3-nitro-7-azaindoles

A mild and efficient dearomatic [3+2] annulation reaction of 3-nitro-7-azaindoles and Morita Baylis Hillman carbonates from isatins was developed catalyzed by DMAP, affording the corresponding polycyclic spirooxindoles containing fused azaindoline architectures and vicinal quaternary centers in excellent yields(up to 96%) with high regio- and diastereoselectivity(dr 19:1). Moderate enantioselectivity(79% ee) was obtained by employing a chiral DMAP-type Lewis base catalyst.     

Efficient Synthesis of a New Type of Baylis–Hillman Adducts and Their Stereoselective Bromination

A new type of Baylis–Hillman adducts derived from chlorovinyl aldehydes were prepared via Vilsmeier reaction of ketones with a bis(trichloromethyl) carbonate (BTC)/DMF system to construct chlorovinyl aldehydes, followed by sonochemical Baylis–Hillman reaction under solvent-free conditions. The stereoselective bromination of these new compounds with a Br₂-Ph₃P system has been achieved efficiently with good to excellent yields under mild conditions.     

Transition-metal-free nucleophilic allylic substitutions of Morita–Baylis–Hillman bromides with aliphatic and aromatic amines

A simple protocol for the preparation of functionalized allylic amines under mild, transition-metal-free conditions from the reaction of Morita–Baylis–Hillman (MBH) bromides with amines is described herein. The treatment of the MBH bromides with various amines in the presence of NaI and Et₃N in aqueous acetone solution and at room temperature affords the corresponding functionalized allyl amines in moderate to good yields (45–87%). The reaction is rapid and carried out at room temperature.     

Synthesis of chiral allene moiety from Morita–Baylis–Hillman adduct of isatin derivatives via Claisen rearrangement

Chiral allenes are synthesized from Morita–Baylis–Hillman adduct of isatin derivatives via Claisen rearrangement for the first time. The chiral 1,3-substituted allene entity is achieved using (R)-but-3-yn-2-ol. The details of the work are elaborately discussed in this letter.     

Asymmetric [3+2]-Cycloaddition of Morita–Baylis–Hillman Carbonates with Maleimides Catalyzed by Chiral Ferrocenylphosphines

New chiral ferrocenylphosphines LB1–LB9 were designed and prepared through simple synthetic approaches. These air-stable ferrocenylphosphines were applied to promote asymmetric [3+2]-cycloaddition of Morita–Baylis–Hillman carbonates with maleimides, among which LB7 was shown to have good catalytic activity to afford the corresponding multifunctional cyclopentenes in up to 59% yield and up to 53% ee under mild reaction conditions. A plausible reaction mechanism was proposed.     

Nickel-catalysed asymmetric SN2′ substitution chemistry of Baylis–Hillman derived allylic electrophiles

Unsymmetrical PhCHCH(CH₂X)(CO₂Me) (X = Cl, OAc) undergoes regioselective α-substitution with AlMe₃ to afford (E)-PhCHCH(Et)(CO₂Me) under Ni(acac)₂ catalysis. On the addition of planar chiral Ferrophite ligands [(R)-CpFe(1,2-C₅H₃Ar{P(OR)₂}) (Ar = Ph, 4-CF₃Ph, 3,5-Me₂Ph, 1-naphthyl; (OR)₂ = 1,1′-binaphthylene, 1,1′-biphenylene)] regioselective methylation γ to the leaving group is possible. It is proposed that the bulky Ferrophite ligand leads to an intermediate nickel allyl species Ni^II(Me)(Ferrophite){η³-PhCHCHCH(CO₂Me)} that adopts a configuration whereby the PhCH terminus of the π-allyl and the Ni–Me are syn leading to good regio (up to 6.4:1) and stereo (up to 94% ee) selectivities.