Diastereoselective synthesis of N-sulfinyl α-aminophosphine sulfides and phosphines

The diastereoselective synthesis of N-sulfinyl α-aminophosphine sulfides and phosphines is reported. These molecules are synthesized by formation of sulfinyl imine followed by diastereoselective addition of a diphenylphosphine sulfide. The product N-sulfinyl α-aminophosphine sulfides can be converted to phosphines through removal of the sulfur by reaction with Raney nickel. Hydrolysis of the sulfinyl group provides an amine that can then be attached to other ligands or structural scaffolds.     

Diastereoselective peroxidation of derivatives of Baylis–Hillman adducts

Cyclic derivatives of Baylis–Hillman adducts were synthesized. Cobalt-catalyzed peroxidation of these cyclic lactones afforded silyl peroxides in diastereomeric ratios ranging from 91:9 to 97:3.     

Diastereoselective synthesis of highly functionalized β2,2,3-substituted amino acids from 4-substituted-1,3-oxazinan-6-ones

1,3-Oxazinan-6-ones were used to generate substituted β^2,2,3-substituted amino acid derivatives. The enolates of 1,3-oxazinan-6-ones were trans-selectively intercepted with electrophiles. This alkylation was subsequently optimized for a one-pot dialkylation to form 5,5-disubstituted oxazinanones. The initial 5-monomethylated compounds could be enolized and then diastereoselectively intercepted with different electrophiles to form differentially 5,5-disubstituted products. The 5,5-dialkylated oxazinanones were then transformed to N-methyl β^2,2,3-substituted amino acids by reductive cleavage. Hydrolysis or solvolysis of the oxazinanones afforded β^2,2,3-substituted amino acids or esters, respectively. The chemistry thus provides access to a range of symmetrical and stereopure β^2,2,3-substituted amino acids and further establishes 1,3-oxazinan-6-ones as useful intermediates.     

Diastereoselective synthesis of chiral α-aminoorganotributyltins via ring-opening of 2-tributylstannyloxazolidines

Reactions of 2-tributylstannyloxazolidines 2a-d (cis or trans), derived from (R)-phenylglycinol protected as N-carbamate, with lithium diorganocuprates in presence of boron trifluoride in diethyl ether provide the corresponding functionalized tributylstannyl-α-aminoalcohols 3-10 with diastereoselectivities close to 85:15 in favour of the (S,R)-isomer. The stereochemical trend is preserved using allyltributyltin as nucleophile and TiCl₂(Oi-Pr)₂ as Lewis acid in dichloromethane. The assignments of the (S,R) or (R,R) configurations in 3-10 were achieved on the basis of physicochemical data combined with a radiocrystallographic structure. Stereochemical preferences were rationalized by consideration of the interactions occurring in the iminium intermediates.     

A catalytic asymmetric ring-expansion reaction of isatins and α-alkyl-α-diazoesters: highly efficient synthesis of functionalized 2-quinolone derivatives

Asymmetric expansion: A catalytic asymmetric ring-expansion reaction of the title compounds occurs in the presence of a Sc(OTf)(3) catalyst bearing an N,N'-dioxide-based ligand. Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl).     

Diastereoselective synthesis of tetrahydroquinolines via a palladium-catalyzed Heck–Suzuki cascade reaction

A method for the diastereoselective synthesis of tetrahydroquinolines via a palladium-catalyzed Suzuki terminated Heck reaction is described. The reaction provides access to tetrahydroquinolines containing both quaternary and tertiary stereocenters. Ligand effects, a rationale for the high level of diastereoselectivity, and a mechanistic hypothesis are discussed.     

Triphenylphosphine-catalysed one-pot synthesis of γ-butyrolactone derivatives and highly substituted enones via reaction of dimethyl acetylenedicarboxylate and aryl aldehydes

The reaction between dimethyl acetylenedicarboxylate and various aryl aldehydes in the presence of triphenylphosphine leads to unsaturated γ-butyrolactone derivatives and highly substituted enones in fairly good yields at room temperature.     

Diastereoselective synthesis of β-amino ketone and acid derivatives by palladium-catalyzed conjugate addition

The first diastereoselective synthesis of β-amino ketone and β-amino acid derivatives by palladium-catalyzed conjugate addition of arylboronic acids to chiral β-enamino ketones and β-enamino esters is reported. The catalytic system employing (S)-4-(tert-butyl)oxazolidin-2-one as the chiral auxiliary in water under an air atmosphere provides β-amino ketone and β-amino acid derivatives in high yields with excellent diastereoselectivity.     

Zirconyl chloride promoted highly efficient solid phase synthesis of amide derivatives

An efficient solid phase route for the synthesis of amide derivatives by the reaction of carboxylic acids with urea in the presence of catalytic amount of zirconyl chloride under microwave irradiation conditions was described.In this way,a range of interesting amide derivatives was obtained in good to excellent yields.The catalyst was recycled with fresh reactants and it gave almost similar results without significant loss of activity up to the third run.     

Friedlander synthesis of highly functionalized isoxazolyl quinoline libraries via addition of C(sp3)–H bond to aldehydes

A novel protocol for ionic liquid (IL)-mediated C(sp³)–H bond functionalization of 3,5-dimethyl-4-nitroisoxazoles 4 to substituted o-amino benzaldehydes 5 was developed in excellent yields. Isoxazolyl aryl ethanones 7 have been synthesized from isoxazolyl aryl ethanol synthon 6. Furthermore, utilizing the later as synthons for IL promoted Friedlander synthesis of highly functionalized isoxazole substituted quinoline libraries 9. The merit of this synthesis is easily available and economical starting materials, effective utilization of all the reactants, and simple workup procedure. It is noteworthy that ionic liquid used in C(sp³)–H bond functionalization and Friedlander synthesis reactions can be recycled and reused five times without significant decrease in activity.     

Diastereoselective synthesis of cis-fused pyrano[4,5-c]pyrrole derivatives via microwave-accelerated intramolecular Knoevenagal hetero Diels–Alder reaction

The synthesis of enantiomerically pure pyrano[4,5-c]pyrroles has been accomplished by the intramolecular hetero Diels–Alder reaction of enantiomerically pure N-allyltetheredalkenyl aldehydes with various 1,3-diones. The reaction led to the formation of cis-fused enantiomerically pure pyrano[4,5-c]pyrroles in excellent yield under mild conditions and the products were characterized by spectroscopic data.     

One-pot,three-component synthesis of highly functionalized 1,3-oxazine derivatives from α,β-unsaturated imine,alkyne, and aldehyde

The 1,4-dipoles generated from imines and DMAD have been shown to react efficiently with benzylaldehyde dipolarphiles in one-pot [4+2] annulation resulting in the diversity oriented synthesis of 1,3-oxazine derivatives in good to excellent yields.     

A highly diastereoselective synthesis of α-hydroxy-β-amino acid derivatives via a Lewis acid catalyzed three-component condensation reaction

A very efficient three-component synthesis of a series of syn α-hydroxy-β-amino esters, obtained in high diastereoselection and yield, was realized starting from an aldehyde, benzylamine, and the ketene silyl acetals derived from Ley's lactones. The synthetic protocol was optimized and the above compounds were obtained without the isolation of intermediates. The origin of the observed diastereoselection was investigated through a computational model of the key reaction step.     

Diels-Alder reaction of α-tropolone and electron-deficient dienophiles prompted by Et3N or silica gel: a new synthetic method of highly functionalized homobarrelenone derivatives

A Diels-Alder reaction of α-tropolone and electron-deficient dienophiles prompted by Et₃N or silica gel was performed. Reaction with the highly reactive dienophile, N-methylmaleimide, proceeded smoothly in the presence of Et₃N or silica gel to yield adducts as a mixture of endo and exo isomers. Both catalysts accelerated endo/exo isomerization of the product, and detailed examination of the reaction using hinokitiol and N-methylmaleimide revealed that isomerization proceeds via an intramolecular path without retro Diels-Alder reaction. Successful cycloaddition reactions were established with six other dienophiles: acrylonitrile, methyl acrylate, ethyl vinyl ketone, dimethyl fumalate, dimethyl malate, and dimethyl acetylenedicarboxylate, and the corresponding adducts were obtained in good to moderate yields.     

Synthesis of highly substituted indene derivatives by Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols

An efficient synthetic method to prepare highly substituted indenes in moderate to excellent yields that relies on Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols under mild conditions is described.     

Selective nitrile oxide dipolar cycloaddition for the synthesis of highly functionalized β-aminocyclohexanecarboxylate stereoisomers

Highly functionalized β-aminocyclohexanecarboxylate regio- and stereoisomers were synthesized from a bicyclic β-lactam by successive regioselective iodolactonization, stereo- and regioselective nitrile oxide cycloaddition, lactone ring-opening and isoxazoline ring-opening.     

Gold-catalyzed synthesis of benzil derivatives and α-keto imides via oxidation of alkynes

An efficient process based on the gold-catalyzed redox reaction has been developed to oxidize 1,2-diarylacetylene or ynamide to 1,2-diaryldiketone or α-keto imide respectively. This process can tolerate a variety of functional groups and affords 1,2-dicarbonyl compounds in excellent yields under mild reaction conditions.     

Expedient synthesis of highly substituted pyrroles via tandem rearrangement of α-diazo oxime ethers

An efficient rhodium-catalyzed synthesis of 2H-azirines and pyrroles has been developed. Novel rearrangement of α-oximino ketenes derived from α-diazo oxime ethers provides 2H-azirines bearing quaternary centers and allows for subsequent rearrangement to highly substituted pyrroles in excellent yields.     

Diastereoselective synthesis of syn-aminoalcohols via contributing CH-π interaction: simple synthesis of (−)-bestatin

¹H NMR and X-ray crystallography studies revealed that a CH-π and chelation control in aromatic aminoaldehydes (1-6) effects a highly diastereoselective addition to afford optically active syn-aminoalcohols (1a-6a). This methodology was applied to the synthesis of (−)-bestatin.