Highly Substituted Isoxazoles: The Baylis-Hillman reaction of substituted 4-isoxazolecarbaldehydes and attempted cyclization to isoxazole-annulated derivatives

In an attempt to understand the effect of position of the formyl group on the efficiency of Baylis-Hillman reaction within isoxazolecarboxaldehydes, the reactions of substituted 4-isoxazolecarboxaldehydes to obtain highly substituted isoxazoles are described. Attempts to obtain isoxazole-annealed derivatives from these Baylis-Hillman adducts involving SNR’-SNAr substitu-tion strategy are also described.

Trifluoroacetic acid: A more effective and efficient reagent for the synthesis of 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones and 3-arylmethyl-2-amino quinolines from Baylis-Hillman derivatives via Claisen rearrangement

Trifluoroacetic acid has been discovered to be a highly effective and efficient reagent for the tandem Claisen rearrangement and cyclisation reaction to yield 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones from compounds obtained from the SN2 reaction between anilines and acetyl derivatives of Baylis-Hillman adducts of acrylates in the presence of DABCO. In contrast similar compounds obtained from the acetyl derivatives of Baylis-Hillman adduct of acrylonitrile on treatment with trifluoroacetic acid directly furnish 3-arylmethyl-2-amino-quinoline via tandem Claisen rearrangement, cylisation and isomerisation.

Studies on the catalytic hydrogenation of Baylis Hillman derivatives of substituted isoxazolecarbaldehydes

Results of the catalytic hydrogenation of Baylis-Hillman adducts obtained from substituted 3-, 4- and 5-isoxazolecarbox-aldehydes and their corresponding acetates in the presence of Raney-Ni and Pd-C are presented. The hydrogenation of Baylis-Hillman adducts of substituted 5-isoxazolecarbaldehydes and 3-isoxazolecarbaldehydes in the presence of Raney-Ni furnishes diastereoselectively syn enaminones over anti and in the presence of boric acid as an additive further enhancement of diastereoselectivity in favor of syn isomer is observed. The Pd-C-promoted hydrogenation of these substrates is also diastereoselective in favor of syn isomer but occurs without the hydrogenolysis of isoxazole-ring. The presence of boric acid as additive in this hydrogenation exhibits no pronounced effect on diastereoselectivity. The Raney-Ni-mediated hydrogenation of Baylis-Hillman adducts of substituted 4-isoxazolecarbaldehydes yield pyridone derivatives and Pd-C-promoted hydrogenation of the same substrate is diastereoselective to afford the anti isomer of the resulting products. The enaminones derived from Baylis-Hillman adducts of 3- and 5-isoxazolecarbaldehydes serve as versatile precursors for '-hydroxy-1, 3-diketones, which undergo acid-catalyzed ring-closure reaction to afford the furanone derivatives in excellent yields

Simple and efficient synthesis of substituted 2-pyrrolidinones, 2-pyrrolones and pyrrolidines from enaminones of Baylis-Hillman derivatives of 3-isoxazolecarbaldehydes

The enaminones, generated from derivatives of appropriately substituted Baylis-Hillman adducts of 3-isoxazolecarbaldehydes undergo intramolecular ring-closure reactions to afford substituted 2-pyrrolidinones, 1,5-dihydro-2-pyrrolones and N-substituted pyrrolidines in good yields.

Alternate, Easy and practical synthesis of allyl amines from acetyl derivatives of Baylis-Hillman adducts using Methanolic Ammonia

A methanolic ammonia-mediated alternate, easy and practical stereoselective synthesis of allyl amines from the acetyl derivatives of Baylis-Hillman adducts is described.

A reinvestigation into the reaction of NH4OAc with acetyl derivatives of Bay-lis-Hillman adducts: Formation of tertiary and secondary allyl amines in-stead of primary allyl amines

A reinvestigation into the reaction between ammonium acetate and the acetyl derivatives of Baylis-Hillman adducts has led us to conclude that the products obtained are tertiary and secondary allyl amines and not the primary allyl amines. The unambiguous assignment of the structure of products using chemical and spectroscopic methods is described

Synthesis and antibacterial evaluation of ureides of Baylis-Hillman derivatives

The synthesis of several 1-(2-cyano-3-aryl-allyl)-3-aryl-urea(thiourea) constructed from the reaction between allyl amines generated from Baylis-Hillman acetates and substituted isocyanates and isothiocyanates has been described. Further their cyclization in the presence of a base led to the formation of 5-arylmethyl-4-imino-3-aryl-3,4-dihydro-1H-pyrimidin-2-ones. All compounds were tested for their antibacterial activity. Few of the compounds showed superior activity or were equipotent to the standard antibacterial agents.

Odorless Preparation Of Thioglycosides And Thio Michael Adducts Of Carbohydrate Derivatives

A generalized, odorless, one-pot methodology has been developed for the preparation of 1,2-trans-thioglycosides and thio-Michael addition products of carbohydrate derivatives through triphenyl phosphine mediated cleavage of disulfides and reaction of the thiolate formed in situ with glycosyl bromides and glycosyl conjugated alkenes.

Medicinal Chemistry of ureido derivatives as Antiinfectives

Ureides are compounds, which essentially incorporate urea as a substructural component either in open or cyclic form. Ureido derivatives are one of the oldest classes of bioactives, widely used as antiinfective agents. Several of these compounds, including aminoquinuride, aminocarbalide, imidurea, cloflucarban, nitrofurazone, urosulfan, viomycin are used in clinical situations. One of the ureides, the triclocarban is compulsorily used as antibacterial agent in cleansing and disinfecting solutions in hospital, household, cosmetics, toys, textile and plastics. It disables the activity of ENR, an enzyme vital for building the cell wall of the bacteria and fungus. Besides, the ureido-penicillins in clinical use there have been several ureido-lactam derivatives which have been reported to exhibit significant antibacterial activity. A urea containing dipeptide TAN-1057A isolated from Flexibacter spp. has potent bioactivity against MRSA. The metal complexes of sulphonyl ureido derivatives are effective antifungal agents by inhibiting the activity of phosphomannose isomerase, a key enzyme in the biosynthesis of yeast cell walls. There have been number of ureides including the cyclic ureas which are potent HIV protease inhibitors and display significant anti-HIV activity. The urea derivative, merimepodip that has been derived using structure based design, is potent inhibitor of IMPDH and is active against Hepatitis-C infection. This review will primarily focus on the significant work reported for this class of compounds including design, synthesis and biological activity.

Significant yield improvement in the stereoselective synthesis of allyl cyanides from Baylis-Hillman derivatives in aqueous medium under the influence of the Phase-Transfer catalyst

The nucleophilic reaction of NaCN with the acetyl derivative of Baylis-Hillman adducts in the presence of a phase-transfer catalyst in aqueous medium stereoselectively affords the corresponding allyl cyanides in a short period and excellent yields.