Novel Synthesis of N‐Methyl Spiropyrrolidines by 1,3‐Dipolar Cycloaddition Reaction of Azomethine Ylides

A series of novel N‐methyl spiropyrrolidines have been synthesized in good yield by the cycloaddition reaction of azomethine ylides generated by a decarboxylative route from sarcosine and paraformaldehyde with conformationally locked s‐trans enone functionality present in the (E)‐3‐arylidene‐4‐chromanone as dipolarophiles. The structure of the title compound was established by spectroscopic techniques.     

Efficient Synthesis of 3‐Pyrrolylquinolines via an 1,3‐Dipolar Cycloaddition/Oxidation Sequence

The synthesis of some new functionalized quinolyl derivatives relies on the 1,3‐dipolar cycloaddition of an azomethine ylide, generated from sarcosine and paraformaldehyde, to quinolyl α,β‐unsaturated esters, followed by oxidation of the pyrrolidinyl moiety to pyrrole with activated MnO₂.     

Synthesis of Novel Carbohydrate Acridinone Derivatives with Potential Biological Activities using 1,3‐Dipolar Cycloaddition

Novel 10‐{[3‐(6‐hydroxy‐2,2‐dimethyltetrahydrofuro[2,3‐d][1,3]dioxol‐5‐yl)‐4,5‐dihydro‐5‐isoxazolyl]methyl}‐9(10H)‐acridinone derivatives (13–16) were synthesized by 1,3‐dipolar cycloaddition using the carbohydrate derivative as dipole and different 10‐allyl‐9(10H)‐acridinone derivatives (9–12) as dipolarophiles. The new cycloadducts as well as the dipolarophiles precursors were characterized spectroscopically.     

Synthesis of Novel Spiroheterocyclic Framework via the Regioselective 1,3‐Dipolar Cycloaddition Reaction of Azomethine Ylides

Abstract

5‐Aryl‐2,10‐bis(arylmethylene)‐2,3,6,7,8,9‐hexahydro‐5H,10H‐cyclohepteno[1,2‐d]thiazolo[3,2‐a]pyrimidin‐3‐ones undergo a regioselective 1,3‐dipolar cycloaddition reaction with the azomethine ylide derived from isatin and sarcosine to give a new class of complex spiropyrrolidines in good yield. X‐ray crystal structure analysis of one of the products confirms the structure and regiochemistry of the cycloadditions.     

Synthesis of a Novel Dispiroheterocyclic Framework via the Regioselective 1,3‐Dipolar Cycloaddition Reaction of Azomethine Ylides

2‐Arylidene‐1,3‐indanediones undergo regioselective 1,3‐dipolar cycloaddition with the azomethine ylide generated from acenaphthenequinone and sarcosine to afford a rare class of complex dispiropyrrolidines in good yield. Single‐crystal X‐ray crystal analysis of one of the products confirms the structure and regiochemistry of the cycloaddition.     

Synthesis of Novel Pyrazolines via 1,3‐Dipolar Cycloadditions of Heterocyclic Isopropenes

An efficient and practical synthesis of novel pyrazoline structures has been achieved through 1,3‐dipolar cycloaddition of the corresponding heterocyclic isopropenes and diazo precursors.     

Versatile Spirocyclic Glycine‐Based Nitrones and Their Highly Stereoselective 1,3‐Dipolar Cycloaddition

A convenient and efficient method for the synthesis of novel spirocyclic nitrones prepared from glycine derivatives is reported. The 1,3‐cycloaddition reactions of the nitrones with alkenes lead to novel isoxazolidines in high yields and with excellent regio‐ and stereoselectivity.     

Double Asymmetric Induction in 1,3‐Dipolar Cycloaddition of Nitrones to 2,3‐Unsaturated Sugar 1,5‐Lactones

1,3‐Dipolar cycloaddition of nitrones 1–3 to the α,β‐unsaturated δ‐lactones, non‐chiral 4, d‐glycero 5, dl‐glycero 5/5ent, d‐erythro 6, and d‐threo 7, provides an interesting example of a double asymmetric induction. In all cases, only the exo approach of reactants was observed. The high preference of anti addition of the nitrones to the terminal acetoxymethyl group in the lactones 5–7 is consistent with previous observations, and can be explained in terms of the axial approach of the nitrone oxygen atom. The 3‐t‐butoxy group of the nitrone plays a similar role. In the case of mismatched pairs, the location of the 4‐acetoxy substituent in the lactone and that of the 4‐t‐butoxy one in the nitrone become decisive for the outcome of the addition. CD‐spectroscopy proved to be an attractive tool to determine the absolute configuration of the cycloadducts.     

The Chemistry of Tetrafluoroallene： One－pot Synthesis of Trifluoromethylindolizines from 1,3－Diiodo－1,1,3,3－tetrafluoropropane by 1,3－Dipolar Cycloaddition

Heating a mixture of 1, 3-diiodo-1, 1, 3, 3-tetrafluoropropane (2), K2CO3, pyridinium bromides (3) in CH3CN at 65℃ for 10 h gives the corresponding trifluoromethylindolizines.     

Synthesis of 5‐Cyano‐1,3‐dioxoalkanes by Reaction of 1,3‐Dicarbonyl Dianions with Bromoacetonitrile

5‐Cyano‐1,3‐dioxoalkanes were prepared by reaction of 1,3‐dicarbonyl dianions with bromoacetonitrile.     

New Method for the Synthesis of 2‐Aza‐1,3‐Butadienes

2‐Aza‐1,3‐butadienes have been synthesized from carbonyl compounds and 1,1,1,3,3,3‐hexamethyl‐disilazane in the presence of cobalt‐containing catalysts. The best yields (up to 95%) were achieved in the case of aldehydes branched in the α-position and 2-methylcyclohexanone. In the case of two α,β‐unsaturated ketones, pyridine derivatives were found as the main products.     

Facile Synthesis of 3,6‐Diaminopyridazine

An efficient two‐step synthesis of 3,6‐diaminopyridazine from 3,6‐dichloropyridazine is reported. In this synthetic procedure, 4‐methoxybenzylamine was used as a nitrogen source to substitute the chloro groups of 3,6‐dichloropyridazine to form N,N′‐bis‐(4‐methoxybenzyl)‐pyridazine‐3,6‐diamine. The 4‐methoxybenzyl groups were then removed by treatment with hydrochloric acid to provide the target 3,6‐diaminopyridazine with an overall yield of 78%.     

Facile Synthesis of 4‐Functionalized Cyclopentenones

1-8-Diazabicyclo[5.4.0]undec-7-ene(DBU)‐catalyzed Michael addition of nitroalkanes to dicyclopentadienone (1) followed by flash vacuum pyrolysis (FVP) provided a high‐yielding synthesis of extremely pure 4‐nitroalkyl cyclopentenones (3). The optimized Nef reaction of the nitro adducts (2) provided 4‐ketoalkyl cyclopentenones (5) in the similar way.     

Facile Synthesis of 2‐Substituted 4‐Azaindoles

A novel and efficient strategy for the synthesis of 2‐substituted 4‐azaindoles from 2‐chloro‐3‐nitropyridine through Pd‐catalyzed Sonogashira cross‐coupling, followed by reduction and heteroannulation on t‐BuOK, is reported.     

Facile Synthesis of New L‐Arginine Derivatives as Substrates for Trypsin‐Like Proteases

Abstract

Facile and efficient synthetic routes for fluorogenic anilides of L‐arginine have been developed. The amide bond formation uses phosphorous oxychloride as a condensing agent. The synthesis is simple, rapid, and affords excellent yields.     

Synthesis of New Spiro[1,4,2-dioxazole-5,3′-indolin]-2′-one by 1,3-Dipolar Cycloaddition

Novel spiro[1,4,2-dioxazole-5,3′-indolin]-2′-one derivatives were synthesized by 1,3-dipolar cycloaddition reactions of the isatin derivative with aryl nitrile oxide. The cycloadducts were characterized by spectral data including ¹H NMR, ¹³C NMR, infrared, mass spectra, and elementary analysis.     

Facile Synthesis of 3,3‐Dialkyl‐6‐phenyl‐imidazopyridinones

A series of novel 3,3‐dialkylated imidazopyridinones bearing 6‐aryl groups were designed as mimetics of active progesterone antagonists, 3,3‐disubstituted‐5‐arylindoles. The four‐step synthetic route is described. The key steps are base‐catalyzed cyclization, base‐catalyzed alkylation, and Suzuki coupling reaction.     

The Chemistry of Tetrafluoroallene:One-pot Synthesis of Trifluoromethylindolizines from 1,3-Diiodo-1,1,3,3-tetrafluoropropane by 1,3-Dipolar Cycloaddition

Heating a mixture of 1, 3-diiodo-1, 1, 3, 3-tetrafluoropropane(2), K_2CO_3, pyridinium bromides (3) in CH_3CN at 65℃ for10 h gives the corresponding trifluoromethylindolizines.     

Catalytic Asymmetric Synthesis of α-Quaternary Proline Derivatives by 1,3-Dipolar Cycloaddition of α-Silylimines

Going pro: The title reaction between α-silylimines and activated olefins proceeds in the presence of a Cu(I) /DTBM-Segphos catalyst system with excellent diastereoselectivity and enantioselectivity. This process provides straightforward access to highly enantioenriched 5-unsubstituted α-quaternary proline derivatives. TMS=trimethylsilyl, DTBM-Segphos=5,5'-bis[di(3,5-di-tert-butyl-4-methoxyphenyl)phosphino]-4,4'-bi-1,3-benzodioxole.     

Soluble Polymer-Supported Synthesis of Pyrazoles via 1,3-Dipolar Cycloaddition Strategy

Rapid parallel liquid-phase synthesis of pyrazoles has first been developed. The 1,3-dipolar cycloaddition between nitrilimines generated in situ and soluble polymer-supported alkynyl or alkenyl dipolarophiles in parallel one-pot fashion gave the corresponding PEG-supported regioisomeric pyrazoles or regiospecific pyrazolines. The latter was assuredly oxidated by DDQ to PEG-supported regiospecific pyrazoles. Cleavage from the support under mild conditions afforded pyrazoles in good yields and high ouritv.