39511-07-4

Tandem oxidative-dehydrogenation of primary alcohols to give a,b-unsaturated aldehydes in one pot are rare transformations in organic synthesis, with only two methods currently available. Reported herein is a novel method using the bench-stable salt methyltriphenylphosphonium perruthenate (MTP3), and a new co-oxidant NEMO&middoPF6 (NEMO = N-ethyl-N-hydroxymorpholinium) which provides unsaturated aldehydes in low to moderate yields. The Ley-Griffith oxidation of (hetero)arylated primary alcohols with N-oxide co-oxidants NMO (NMO = N-methylmorpholine N-oxide)/NEMO, is expanded by addition of the N-oxide salt NEMO&middoPF6 to convert the intermediate saturated aldehyde into its unsaturated counterpart. The discovery, method development, reaction scope, and associated challenges of this method are highlighted. The conceptual value of late-stage dehydrogenation in natural product synthesis is demonstrated via the synthesis of a polyene scaffold related to auxarconjugatin B.

The invention discloses a method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and a diphosphine ligand used in the method. According to the invention, indole-substituted phosphoramidite diphosphine ligand which is stable in air and insensitive to light is synthesized by utilizing a continuous one-pot method, and the indole-substituted phosphoramidite diphosphine ligand and a rhodium catalyst are used for jointly catalyzing to successfully achieve a hydroformylation reaction of aromatic terminal alkyne and terminal conjugated eneyne under the condition of synthesis gas for the first time, so that an olefine aldehyde structure compound can be rapidly and massively prepared, and particularly, a polyolefine aldehyde structure compound which is more difficult to synthesize in the prior art can be easily prepared and synthesized, and a novel method is provided for synthesis and modification of drug molecules, intermediates and chemical products.

A simple yet highly effective approach toward enantioselective synthesis of trans-3,4-disubstituted glutarimides from readily available starting materials is developed using oxidative N-heterocyclic carbene catalysis. The catalytic reaction involves a formal [3 + 3] annulation between enals and substituted malonamides enabling the production of glutarimide derivatives in a single chemical operation via concomitant formation of C-C and C-N bonds. The reaction offers easy access to a broad range of functionalized glutarimides with excellent enantioselectivity and good yield. Synthetic application of the method is demonstrated via formal synthesis of (?)-paroxetine and other bioactive molecules.

α,β-unsaturated aldehydes have been traditionally used in LUMO lowering asymmetric aminocatalysis (iminium catalysis), while the use of saturated aldehydes as substrates in this type of catalysis has been elusive, until recently. Herein, we demonstrate that organic, single-electron oxidants in the presence of diarylprolinol silylether type catalysts serve as effective tools for the transformation of electron rich enamines to iminium ions which partake in a subsequent Diels-Alder reaction. This enantioselective one-pot transformation represents the first example of saturated aldehydes being used in domino Diels-Alder reaction processes and demonstrates the power of this protocol for construction of stereo-defined chiral compounds and building blocks. (Figure presented.).

Finding novel cholinesterase inhibitors that would be able to cross the blood–brain barrier, have favorable pharmacokinetic parameters, and reduce hepatotoxicity along with other side effects has been the main focus of investigations dealing with Alzheimer disease. In this study we evaluated cholinesterase inhibitory and antioxidant activity of seven oxazole derivatives. These compounds have been efficiently and sustainably prepared by photochemical electrocy-clization reaction. Various naphthoxazoles have been previously investigated as potential antibacterial, antituberculosis, and anticancer agents. They have also been tested for antioxidant activity, but never for cholinesterase inhibitory activity. Among the tested oxazole derivatives, fused heterobenzoxazole compounds with pyridine and thiophene moiety, oxazolo[5,4-h]isoquinoline, thieno[2’,3’:5,6]benzo[1,2-d]oxazole, and thieno[3’,2’:5,6]benzo[1,2-d]oxazole, showed the greatest potential for both cholinesterase inhibitory and antioxidant activity. Among them, thieno[2’,3’:5,6]benzo[1,2d]oxazole was found to be the best one.

An organocatalytic [3 + 3] benzannulation to access polysubstituted benzenes from readily available α,β-unsaturated aldehydes and 1,3-bis(phenylsulfonyl)propene or 4-sulfonylcrotonates is described. The key reaction step is considered to be the iminium ac

A one-pot, two-step l-proline-mediated stereoselective α-C(sp2)–H fluorination of α,β-unsaturated aldehydes towards their corresponding (Z)-α-fluoro-α,β-unsaturated aldehydes has been developed. The first step utilises Selectfluor as a fluorinating agent in CH3NO2/MeOH forming (Z)-α-fluoro-α,β-unsaturated aldehydes and their corresponding dimethyl acetals through methoxyfluorination-elimination. In the second step, water is added to promote the hydrolytic cleavage of the dimethyl acetals. The obtained (Z)-α-fluoro-α,β-unsaturated aldehydes were smoothly reduced to the corresponding alcohols by using NaBH4.

We have developed an easy and practical method for the synthesis of α,β-unsaturated oximes and nitriles from readily available propargylic alcohols with hydroxylamine hydrochloride (NH2OH·HCl) under metal-free conditions. By using or not using p-toluenesulfonyl chloride (p-TsCl) as the dehydrating promoter, the desired nitriles or oximes could be obtained, respectively via a three-step one-pot or two-step one-pot process in moderate to excellent yields with good functional group compatibility.

Regioselective synthesis of 4-hydroxybiphenyl-2-carboxylates via the base-mediated oxygenative [3 + 3] benzannulation reaction of α,β-unsaturated aldehydes and γ-phosphonyl crotonates is reported. A hydroxyl group is installed in the final product on the originally phosphorus-bound carbon via a novel oxygenative and dehydrogenative transformation. The reaction proceeds rapidly in an open flask, uses atmospheric oxygen as an oxidant, and affords good yields of substituted biaryl phenols. (Chemical Equation Presented).

In this work, the phosphine-catalyzed annulation reactions between modified allylic derivatives and polar 1,1-dicyano-1,3-dienes have been studied. In the catalysis of PPh3 (20 mol%), a [4+1] annulation reaction is realized between a series of 1,1-dicyano-2,4-diaryl-1,3-dienes and ethoxycarbonyl- activated allylic acetate, producing polysubstituted cyclopentenes in modest to excellent yields. It is also observed that the substituents of both 1,3-dienes and allylic derivatives have a significant influence on the annulation mode: under the catalysis of PPh3 or PBu3 (20 mol%), regioselective [3+2] annulation products are formed from differently substituted substrates. Chemoselective phosphine-catalyzed [4+1] and [3+2] annulations of modified allylic derivatives and polar 1,3-dienes have been realized, and substituent effect on the annulation mode was first observed. Copyright

Three stereogenic centers in a row: The unconventional activation of enal compounds mediated by an N-heterocyclic carbene (NHC) has generated three consecutive reactive carbon centers that undergo highly regio- and stereoselective annulations with di(enone)s to generate benzotricyclic products containing multiple stereogenic centers (see scheme).

The luminescence lifetimes (in CH3CN at room temperature) and electrochemical potentials (in CH3CN) of a range of mono- and bis(bidentate) 2,2′-bipyridine-capped oligothiophene-bridged Ru II complexes based on the 6-(2-thienyl)-2,2′-bipyridine and 4-(2-thienyl)-2,2′-bipyridine motifs have been measured. The redox potentials occurred in a very narrow range and showed only small shifts from that of [Ru(bpy)3]2+, which indicates that the inductive effects of the substituents on the 2,2′-bipyridine ligands are very similar across this series. In the complexes that incorporated a bithiophene moiety the oxidation of the bithienyl group occurred at higher potentials than the metal-centered RuIII/II oxidation. No or very weak interaction between the metal cores in the dinuclear complexes was observed. It was found that the luminescence lifetimes of the complexes where the attachment point of the oligothiophene bridge is in the 4-position of a 2,2′-bipyridine ligand were extended compared to [Ru(bpy)3]2+, whereas the luminescence was very short-lived (30 ns) or completely quenched in the complexes where the oligothiophene bridge was attached in the 6-position. The difference in lifetimes is probably due to steric interactions between the thienyl bridge and the auxiliary bipyridyl ligands, resulting in disturbances in coordination symmetry of the metal core. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

The electrochemical and photophysical properties for a range of tris(2,2′-bipyridine)ruthenium(II) complexes in which a thiophene substituent is attached to one of the bipyridine ligands by either a pendant or a fused mode have been determined. The fused mode of attachment eliminates torsional movement between the thiophene unit and the chelating bipyridine, thereby offering optimal overlap between the ?-systems of the chelating unit and the attached thiophene unit. The electrochemical properties of these complexes were found to be similar; however, the luminescence lifetimes and intensities (in CH3CN at room temperature) were found to be correlated to the mode of attachment. The longest luminescence lifetime was observed for the complex [Ru(bpy)2{4-(thiophen-2-yl)-2,2′-bipyridine}] 2+ (3000 ns), as compared to the prototypic [Ru(bpy) 3]2+ (1745 ns). This complex also had the highest quantum yield (0.045). In the four isomeric complexes, where the thiophene ring was fused to the b or c face of the pyridine ring, the lifetimes fell in the interval 275-1510 ns, and the quantum yield ranged between 0.0047 and 0.014. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

A novel cascade cyclisation protocol has been developed which 'zips up' two rings to form new tetracycles. In the protocol, treatment of vinyl bromides and iodides with hexamethylditin (Me3Sn· yields intermediate vinyl radicals which undergo 5-exo cyclisation onto nitrile groups to yield intermediate iminyl radicals. The iminyl radicals can undergo 6-endo cyclisation (or 5-exo followed by neophyl rearrangement) to yield tetracyclic π-radicals which lose hydrogen (H·) in an H-abstraction step. Methyl radicals, generated from the breakdown of trimethylstannyl radicals (Me3Sn·), are proposed as a possible H-abstractor for this final oxidative step. The protocol has been used to synthesise the tetracyclic rings A-D (tetracycle indolizino[1,2-b]quinolin-9(11H)-one) of the anticancer alkaloids camptothecin, mappicine, nothapodytine B and nothapodytine A. The protocol has also been applied to the synthesis of analogues of camptothecin in which ring A has been replaced by thiophene (8,10-dihydrothieno[2′,3′:5,6]pyrido[2,3-a]indolizin-8-one) and ring D by pyrrole (10H-pyrrolizino[1,2-b]quinoline) and benzene (11H-indeno[1,2-b]quinolin-11-one).

The reduction of 1,1-difluoro-1-alken-3-ols with lithium tetrahydroaluminate is described. 1-Fluoro-1-alken-3-ols obtained can be transformed to enals or difluoromethylated allylic derivatives.

The Cr=C bonds of aryl- and alkenyl(ethoxy)carbene chromium complexes 1a-d are hydrolysed under mild reaction conditions with high chemoselectivity in presence of hexamethylenetetramine (urotropine), 2, to give aldehydes 4a-d and (urotropine)Cr(CO)5, 3.The alkynyl(ethoxy)carbene chromium complex 1e reacts with urotropine in a completely different fashion and forms a binuclear (β-amino)vinylcarbene complex, 5, by fragmentation of the urotropine skeleton.

Allyl trimethylsilyl ether reacts with aryl iodides in the presence of palladium acetate and lithium chloride to afford selectively β-aryl (E)-α,β-unsaturated carbonyl compound.