Polyethylene glycol (PEG) as an efficient recyclable medium for the synthesis of β-amino sulfides

Aziridines undergo ring opening readily with various thiols in the presence of polyethylene glycol (PEG) to afford the corresponding β-amino sulfides in high yields with good regioselectivity under mild and neutral conditions. The PEG can be recovered and reused.     

Poly(ethylene glycol) (PEG) as a reusable solvent medium for organic synthesis. Application in the Heck reaction

[reaction: see text] PEG has been used as a solvent medium for regioselective Heck reactions with easy recyclability of solvent and Pd catalyst for the first time.     

Polyethylene glycol (PEG-400): an efficient and recyclable reaction medium for the synthesis of pyrazolo[3,4-b]quinoline derivatives

A simple, efficient, and eco-friendly synthetic protocol has been developed via one pot three-component reaction between aldehyde, amino pyrazole, and 1,3-cyclohexanedione by using recyclable polyethylene glycol (PEG)-400 as a reaction medium. Utilizing this protocol a variety of pyrazolo[3,4-b]quinoline derivatives were synthesized in excellent yields.     

A straightforward preparation of benzo[f]naphtho[b][1,4]oxazepines from TNT

2,4,6-Trinitrotoluene readily reacts with 1-nitroso-2-naphthol to afford 9,11-dinitrobenzo[f]naphtho[2,1-b][1,4]oxazepine. The nitro groups of the latter undergo displacement by O- and S-nucleophiles with preferential substitution of the 11-NO₂ (peri-nitro group). The structures of the substitution products are confirmed by X-ray diffraction and ¹H NMR NOE experiments.     

Synthesis of polyfluorodibenz[b,f][1,4]oxazepines by the cyclization of 2-[(polyfluorobenzylidene)amino]phenols

Thermolysis of 2-[(polyfluorobenzylidene)amino]phenols in ethanol in the presence of triethylamine affords the corresponding fluorinated dibenz[b,f][1,4]oxazepines in moderate to high yields. The structures of 2-[(2,3,4,5,6-pentafluorobenzylidene)amino]phenol and 1,2,3,4-tetrafluorodibenzo[b,f][1,4]oxazepine have been determined by single-crystal X-ray diffraction.     

Functionalized fluorinated arylethers by ring-opening of 1,2,3,4-tetrafluorodibenz[b,f][1,4]oxazepine

Treatment of 1,2,3,4-tetrafluorodibenz[b,f][1,4]oxazepine with acetyl or benzoyl chloride produces the fluorinated aryl ethers bearing amide and aldehyde functionalities, RCONHC₆H₄-2-OC₆F₄CHO-2 (2a R=Ph; 2b R=Me). The structures of intermediate compounds produced by addition of acid chloride across the imine bond and by partial hydrolyis of the resulting chlorine-containing compound have been determined.     

Polyethylene glycol (PEG-400) as an efficient and recyclable reaction medium for one-pot synthesis of polysubstituted pyrroles under catalyst-free conditions

Polyethylene glycol (PEG) was found to be an inexpensive non-toxic and effective medium for the one-pot synthesis of highly functionalized pyrroles. Utilizing this protocol various pyrrole derivatives were synthesized in excellent yields. Environmental acceptability, low cost, high yields, and recyclability of the PEG are the important features of this protocol.     

Poly(ethyleneglycol) (PEG): a rapid and recyclable reaction medium for the DABCO-catalyzed Baylis-Hillman reaction

PEG (400) has been used as a rapid and recyclable reaction medium for the Baylis-Hillman reaction with the conventional basic catalyst DABCO (20 mol %) with very good yields of products. Recyclability is achieved with no further addition of DABCO to the reaction medium for over four runs without substantial loss in yields. Incidentally, DABCO is recycled for the first time in this transformation.     

Palladium-catalyzed asymmetric hydrogenation of dibenzo[b,f][1,4]thiazepines activated by Brønsted acid

An efficient and facile route to chiral dihydrodibenzothiazepines has been successfully developed via palladium-catalyzed asymmetric hydrogenation of the dibenzothiazepines with Brønsted acid as activator with up to 94% ee.     

Polyethylene glycol (PEG-400): an efficient green reaction medium for the synthesis of benzo[4,5]imidazo[1,2-a]-pyrimido[4,5-d]pyrimidin-4(1H)-ones under catalyst-free conditions

A simple and an efficient eco-friendly methodology has been developed for the synthesis of benzo[4,5]imidazo[1,2-a]-pyrimido[4,5-d]pyrimidin-4(1H)-ones in excellent yields under catalyst-free-conditions using inexpensive and non-toxic polyethylene glycol (PEG-400) medium. This new protocol offers an environmental acceptability, shorter reaction time, room temperature, low cost, high yields, and recyclability of the PEG-400 medium are the important features. This method provides a green and much improved protocol over the existing methods.     

An efficient synthesis of spiro[dibenzo[b,i]xanthene-13,3′-indoline]-pentaones and 5H-dibenzo[b,i]xanthene-tetraones

Spiro[dibenzo[b,i]xanthene-13,3′-indoline]-pentaones and 5H-dibenzo[b,i]xanthene-tetraones are synthesized from the condensation of 2-hydroxynaphthalene-1,4-dione with isatins or aldehydes.     

Synthesis and molecular and electronic structure of dibenz(b,f)-1,4-oxazepine

Russian National Scientific-Research Institute of Organic Chemistry and Technology. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 1, pp. 197–201, January–February, 1995.     

Ugi three-component coupling reaction for the synthesis of 2-(6-oxo-11-phenyl-7,8-dihydrobenzo[b]pyrrolo[1,2-d][1,4]diazocin-5(6H)-yl)-2-phenylacetamide derivatives

A three-component, four center Ugi reaction of 3-(1-(2-aminophenyl)-5-phenyl-1H-pyrrol-2-yl)propanoic acid with aromatic aldehyde and t-butyl isocyanide has been achieved to produce a novel class of N-tert-butyl-2-(6-oxo-11-phenyl-7,8-dihydrobenzo[b]pyrrolo[1,2-d][1,4]diazacine-5(6H)-yl)-2-phenylacetamides in moderate to good yields.     

Palladium-mediated approach to dibenzo[b,e][1,4]diazepines and benzopyrido-analogues. An efficient synthesis of tarpane

An original synthetic route toward dibenzo[b,e][1,4]diazepin-11-ones and analogues pyridobenzodiazepinones has been developed. The method relies upon an intramolecular amination process between an (hetero)aryl halide and the appropriate aniline moiety.     

A new synthesis of benzo[b]thiophenes utilizing an interrupted Pummerer reaction

A convenient synthesis of 3-arylbenzo[b]thiophenes utilizing an interrupted Pummerer reaction of 2-(1-arylvinyl)phenyl ethyl sulfoxides is described. Thus, treatment of these sulfoxides, which were readily prepared from 2-sulfanylphenyl ketones or 2-fluoro-5-methoxybenzaldehyde, with acetic anhydride at 100 °C afforded 3-arylbenzo[b]thiophenes in reasonable yields.     

Thermal cyclization of N-[2-(2-propenyl)-1-naphthyl] ketenimines: intramolecular Diels-Alder reaction versus [1,5] hydrogen migration. Synthesis of dibenz[b,h]acridines and benzo[h]quinolines

The thermal treatment of N-(2-propenyl)-1-naphthylamines provided the expected aza-Claisen rearranged products, 2-(2-propenyl)-1-naphthylamines and benz[g]indoles, these last derived from an intramolecular hydroamination reaction on those primary products. The 2-(2-propenyl)-1-naphthylamines were converted into their triphenylphosphazene derivatives, which by aza-Wittig reaction with disubstituted ketenes yielded N-[2-(2-propenyl)-1-naphthyl] ketenimines. The heating of these ketenimines in boiling toluene induced their cyclization either via an intramolecular Diels-Alder reaction, to afford dibenz[b,h]acridines, or via [1,5] hydrogen migration from the sp³ carbon atom of the propenyl substituent to the central carbon atom of the ketenimine fragment, followed by a 6π electrocyclic ring closure, to give benzo[h]quinolines.     

A facile synthesis of benzo[b][1,4]thiazepine derivatives by palladium acetate catalyzed reaction

The preparation of steroid/nonsteroid fused benzo[b][1,4]thiazepines and 2-arylsubstituted benzo[b][1,4]thiazepines is described from Pd(OAc)₂ catalyzed reaction of steroidal/nonsteroidal β-halovinyl aldehydes and 2-aminothiophenols in DMF under heating condition.     

Is samoquasine A indeed benzo[f]phthalazin-4(3H)-one? Unambiguous, straightforward synthesis of benzo[f]phthalazin-4(3H)-one and its regioisomer benzo[f]phthalazin-1(2H)-one

In search for the structural elucidation of samoquasine A, a natural product isolated from the seeds of Annona squamosa L., two benzo[f]phthalazinone isomers have been synthesized. The synthetic pathway followed to build up these skeletons is based on the combination of two Suzuki reactions on a pyridazinone precursor and a ring closure reaction via a condensation reaction. ¹H NMR data of the synthesized compound allowed to establish that the structure of the natural product samoquasine A is not benzo[f]phthalazin-4(3H)-one, as previously suggested.     

Poly(ethylene glycol)-supported copper(II) triazacyclononane: an efficient, recoverable, and recyclable catalyst for the cleavage of a phosphodiester

The triazacyclononane macrocycle has been linked to the soluble polymer monomethoxy poly(ethylene) glycol and its copper(II) complex efficiently catalyzes the hydrolysis of a model phosphodiester. The catalyst, easily recovered from the water solution, shows no appreciable loss of activity when recycled three times.     

A simple and green procedure for the conjugate addition of thiols to conjugated alkenes employing polyethylene glycol (PEG) as an efficient recyclable medium

Polyethylene glycol (PEG) is found to be an inexpensive, nontoxic, environmentally friendly reaction medium for the conjugate addition of thiols to conjugated alkenes to afford the corresponding adducts in excellent yields under mild and neutral conditions. Products of undesirable side reactions resulting from polymerization are not observed. The use of PEG avoids the use of either acid or base catalysts for this conversion and moreover PEG can be recovered and reused.