Studies toward the construction of substituted piperidine-2-ones and pyridine-2-ones from Baylis-Hillman adducts: discovery of a facile synthesis of 5-methyl-4-oxo-6-aryl-3-aza-bicyclo[3.1.0]hexane-1-carboxylates

Studies toward the construction of functionalized piperidone derivatives from derivatives of Baylis-Hillman adducts are described. Interestingly the 6-oxo-4-aryl-piperidine-3-carboxylates generated during the study serve as precursor for the facile synthesis of 4-oxo-6-aryl-3-aza-bicyclo[3.1.0]hexane-1-carboxylates.     

Regioselective construction of polysubstituted pyridine ring from Baylis-Hillman adducts via sequential introduction of tosylamide, Michael reaction, aldol condensation, and elimination of TsH

Facile synthetic method of polysubstituted pyridine derivatives was developed starting from the Baylis-Hillman adducts. The reaction involved sequential introduction of tosylamide, Michael addition, aldol condensation, elimination of p-toluenesulfinic acid, and isomerization process.     

Sequential Baylis-Hillman reaction and radical cyclization of furanose derivatives: expeditious approach to enantiopure benzo-fused nine-membered oxacycles

A regioselective 9-endo-trig aryl radical cyclization of d-glucose derived diastereomeric Baylis-Hillman reaction products with Bu₃SnH led to highly functionalized tricyclic benzannulated ethers incorporating cis- and trans-9,5 bicyclic systems in good yields. Degradation of one of the products afforded an enantiopure multifunctionalized benzoxonine derivative.     

Baylis-Hillman chemistry: synthesis of cis- and trans-α-methylene-γ-lactones

syn-Homoallylic alcohols prepared from Baylis-Hillman adducts react with CBr₄/PPh₃ to give trans-α-methylene-γ-lactones. Notably, the same alcohols yield the cis-α-methylene-γ-lactones in the presence of traces of p-toluenesulfonic acid.     

Diastereoselective Baylis-Hillman reaction: first use of chiral 2,3-epoxy aldehydes as novel electrophiles

Chiral 2,3-epoxy aldehydes have been effectively utilized for the first time as novel electrophiles in Baylis-Hillman reactions with activated alkenes to result in densely functionalized adducts in good yields (61-80%) and in moderate to good diastereoselectivities (40-72% de).     

An unexpected inversion of enantioselectivity in the proline catalyzed intramolecular Baylis-Hillman reaction

A highly enantioselective proline catalyzed intramolecular Baylis-Hillman reaction of hept-2-enedial is reported. Addition of imidazole to the mixture results in an unusual inversion of enantioselectivity.     

Baylis-Hillman adducts between pyridine carboxaldehyde derivatives and cyclic enones

Baylis-Hillman (BH) adducts were synthesized using pyridinecarboxaldehyde derivatives and cyclic enones. The Baylis-Hillman reaction was examined by employing various organic tertiary bases and solvents. It was observed that DBU in MeOH as well as imidazole and N-methylimidazole in aqueous MeOH are very effective. These pyridinecarboxaldehydes were reactive and efficient towards the Baylis-Hillman reaction and the resulting adducts are highly stable. The crystal structure for one of the BH adducts was determined.     

A cyclative cleavage approach to solid-phase synthesis of annulated pyrimidinones using Baylis-Hillman derivatives

An efficient and robust solid-phase synthesis of 6-substituted-2,5,6,8-tetrahydro-3H-imidazo[1,2-a]pyrimidin-7-ones, 3-substituted-1,3,4,6,7,8-hexahydro-pyrimido[1,2-a]pyrimidin-2-ones and 3-substituted-3,4,6,7,8,9-hexahydro-1H-pyrimido[1,2-a][1,3] diazepin-2-ones from the acetates of Baylis-Hillman adducts employing Michael addition of diamines followed by intramolecular cyclization with cyanogen bromide and, finally, base promoted cyclative cleavage has been developed. The procedure is validated through an automated parallel synthesis of a small library of fourteen compounds of the 3H-imidazo[1,2-a]pyrimidin-7-one series.     

A facile one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids from unactivated Baylis-Hillman adducts and a simple access to some important insect pheromones

An efficient one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids has been accomplished by treatment of unactivated Baylis-Hillman adducts, 3-hydroxy-2-methylenealkanoates, with Al-NiCl₂·6H₂O in methanol at room temperature followed by hydrolysis. The method has been applied to the synthesis of three important insect pheromones, (4S,2E)-2,4-dimethyl-2-hexenoic acid, (+)-(S)-manicone and (+)-(S)-normanicone.     

Studies on montmorillonite K10-microwave assisted isomerisation of Baylis-Hillman adduct. Synthesis of E-trisubstituted alkenes and synthetic application to lignan core structures by vinyl radical cyclization

The isomerisation of acetates from the Baylis-Hillman adducts with Mont.K10 clay-microwave combination furnished E-trisubstituted alkenes in high yield. The simple Baylis-Hillman adducts with trimethyl orthoformate and unsaturated alcohols under clay catalytic condition gave densely functionalised-isomerized products under solvent free condition. Application of the propargyl derivatives thus obtained from the isomerisation of the Baylis-Hillman adducts with propargyl alcohol has been demonstrated in the synthesis of lignan core structures by tri-n-butyltin hydride mediated vinyl radical cyclization.