Two-step syntheses of 2,4,6-triisopropylbenzenesulfonyl aziridines

In a continuing study on the α-lithiation of N-tosyl aziridines, it is reported that ortho-lithiation of the N-tosyl group is occurring under typical α-lithiation conditions (s-BuLi/PMDETA). Thus, a simple, two-step synthesis of N-2,4,6-triisopropylbenzenesulfonyl aziridines was optimised. The route involves epoxide ring opening using a sulfonamide, mesylation and base-mediated ring closure. The scope and limitations of this route were assessed and five new N-2,4,6-triisopropylbenzenesulfonyl aziridines were prepared in good yields. Since this method was unsuitable for the preparation of cyclooctene aziridine, an alternative two-step method was developed. This method involved aminobromination of cyclooctene using NBS/2,4,6-triisopropylbenzenesulfonamide.     

Heteroatom transfer to alkenes by N-protected-oxaziridines: new reaction pathways and products

N-Alkoxycarbonyl- and N-carboxamido-oxaziridines are shown to react with aromatic alkenes to give epoxide, aziridine or hydro-oxidation products, in ratios depending on the oxaziridine structure. Chiral oxaziridines can effect epoxidation and hydro-oxidation with promising levels of asymmetric induction.     

Small ring constrained peptidomimetics. Synthesis of epoxy peptidomimetics, inhibitors of cysteine proteases.

Different dipeptide analogues containing an oxirane ring in the place of the peptidic bond were prepared starting from naturally occurring amino acids. N-Fmoc-amino aldehydes were transformed into the corresponding methoxyvinyl derivatives through a Wittig reaction, and the addition of PhSeCl gave a series of different alpha-phenylselenyl aldehydes. Mukajiama reaction with silylketene acetals gave an intermediate product that was finally transformed into the desired oxiranyl peptidomimetics. Following this strategy we were able to control three new contiguous stereocenters starting from the enantiomerically pure amino acid. The dipeptide analogues could be used in SPPS on a SASRIN resin as the final epoxides were relatively unstable under acidic conditions. Moreover the synthesis of the single dipeptide mimetics was carried out on solid phase to generate a small library of epoxy peptidomimetics. Some of the products prepared in this work resulted as time-dependent reversible inhibitors of cysteine protease.     

Synthesis and investigation of aziridino dioximes

The reactions of chloroglyoximes with substituted aziridines were investigated. In the case of donor substituents in the aziridine the reaction takes place with the formation of anti-aziridino dioximes, while the formation of furoxanoglyoximes is also observed when electron-acceptor substituents are present. Aziridinofuroxans were obtained by oxidation of the aziridino dioximes. The barrier to inversion of the nitrogen atom in the aziridinofuroxans is 12.0 kcal/mole. The expansion of the aziridine ring of the aziridino dioximes, which leads to the formation of 1,2,4-oxadiazines, was investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 488–494, April, 1982.     

Synthesis of nitrocyclopropyl peptidomimetics

Nitrocyclopropanation of amino-acid derived enones has led to a series of cyclopropyl peptidomimetics suitable for further elaboration to compounds with the potential for biological activity.     

离子交换法从APT结晶母液中回收钨酸钠

用弱碱大孔离子交换树脂Ｄ３５４在微酸条件下吸附母液中钨，用１０％的苛性钠进行解吸好可获得浓钨酸钠溶液。该法简单而经济。     

An efficient protocol for regioselective ring opening of epoxides using sulfated tungstate: application in synthesis of active pharmaceutical ingredients atenolol,propranolol and ranolazine

Sulfated tungstate was found to be a new and highly efficient catalyst for opening of epoxide rings by amines to give β-amino alcohols with high regioselectivity. Various advantages associated with this novel and environmental friendly protocol include solvent-free conditions, short reaction times, high product yields, simple workup procedure and easy recovery and reusability of the catalyst. This protocol has been applied for the synthesis of active pharmaceutical ingredients atenolol, propranolol and ranolazine.     

Strain-Release Driven Epoxidation and Aziridination of Bicyclo[1.1.0]butanes via Palladium Catalyzed σ-Bond Nucleopalladation

The development of preparative methods for the synthesis of four-membered carbocycles is gaining increasing importance due to the widespread utility of cyclic compounds in medicinal chemistry. Herein, we report the development of a new methodology for the production of spirocyclic epoxides and aziridines containing a cyclobutane motif. In a two-step one-pot process, a bicyclo[1.1.0]butyl sulfoxide is lithiated and added to a ketone, aldehyde or imine, and the resulting intermediate is cross-coupled with an aryl triflate through C−C σ-bond alkoxy- or aminopalladation with concomitant epoxide or aziridine formation. After careful optimization, a remarkably efficient reaction was conceived that tolerated a broad variety of both aromatic and aliphatic substrates. Lastly, through several high yielding ring-opening reactions, we demonstrated the excellent applicability of the products as modular building blocks for the introduction of three-dimensional structures into target molecules.     

Sodium Tungstate: The First Application as Non‐oxidative Catalyst in Organic Synthesis

A convenient synthesis of some pyranocoumarins was described via a one‐pot, three‐component reaction of 4‐hydroxyxoumarin, malononitrile and different aromatic aldehydes in the presence of sodium tungstate. This is the first application of sodium tungstate as non‐oxidative catalyst in organic reactions. Simple operation, use of readily available starting materials, good to excellent yields and short reaction times are the advantages of this method for the synthesis of these biologically important products.     

Chiral Aziridines—Their Synthesis and Use in Stereoselective Transformations

The preparation of enantiomerically pure compounds is one of the major areas of organic chemistry. Much emphasis is placed on the elaboration of naturally occurring starting materials and on the development of techniques for enantio-selective transformations of achiral substrates. In this field, chiral aziridines form an attractive class of compounds, since they are available in enantiomerically pure (or highly enriched) form by a variety of procedures and can be used for asymmetric synthesis in a number of different ways. The chemistry of aziridines is dominated by ring-opening reactions, the driving force for which is relief of ring strain. By suitable choice of sub-stituents on the carbon and nitrogen atoms, excellent stereo- and regiocontrol can be attained in ring-opening reactions with a wide variety of nucleophiles, including organometallic reagents; this makes chiral aziridines useful as substrates for the synthesis of important biologically active species including alkaloids, amino acids, and /Mactam antibiotics. Substrate-controlled diastereo-selective synthesis is also possible by use of aziridines as removable chiral auxiliaries, while metalation at a ring carbon atom allows aziridines to be used as chiral reagents for asymmetric synthesis. Chiral bisaziridines can act as ligands for transition metals, and applications in the challenging field of enantioselective catalysis can be envisioned. Today, the exclusion of three-membered carbo- and heterocycles from the arsenal of the organic chemist is inconceivable.

1 H. Heimgartner, Angew. Chem. 1991 , 103, 271; Angew. Chem. Int. Ed. Engl. 1991 , 30, 238.

     

Sm掺杂的红色荧光粉的制备及发光性能研究

采用高温固相法合成了Ca3Gd2WO9/xSm3＋系列红色荧光材料。研究了合成样品的最佳烧结温度和时间分别为1 100℃和3 h,讨论了Sm3＋的掺杂浓度对Ca3Gd2WO9/x Sm3＋发光强度的影响,当x为1.0%（摩尔分数）时,样品的相对发光强度达到最大值。测量了荧光粉的X射线衍射谱和荧光光谱。结果表明,该样品能够被434 nm的可见光有效激发,主发射峰位593 nm附近,对应于Sm3＋的4G5/2→6H7/2跃迁,可作为白光发光LED的红色发光材料。     

Synthesis of beta-lactam scaffolds for ditopic peptidomimetics

[reaction: see text] Ring opening of alpha-substituted-alpha-methoxycarbonyl-N-nosylaziridines provides a practical access to enantiopure alpha,alpha'-disubstituted beta-lactam scaffolds, novel types of ditopic reverse turn surrogates. The procedure is general, short, and high yielding and starts from handy alpha-substituted serinates and alpha-amino acid derivatives.     

A Facile Synthesis of 1,1,6-Trimethyl 1,2-Dihydronaphtalene

an easy two-step preparation of 1,1,6-trimethyl 1,2-dihydronaphtalene from α-ionone via 1,1,6-trimethyl 1,2,3,4-tetrahydronaphtalene is described.     

Synthesis and photoreactions of polyesters containing triazene and cinnamylidene malonyl units

The synthesis and photoreactions of polyesters containing the photolabile triazene group (Ph NN NR₂) as well as photocrosslinkable units based on substituted cinnamylidene malonyl moieties are reported. The polyesters were obtained by reacting a triazene containing difunctional alcohol with different substituted cinnamylidene malonic acid dichlorides. Irradiation at λ > 395 nm enables selective photocrosslinking of the cinnamylidene malonyl ester units via [2+2]π‐cycloaddition without affecting the triazene units. The photocrosslinking reaction of the triazene containing polyesters as well as triazene‐free reference polyesters were investigated by UV and IR spectroscopy. After selective photocrosslinking the irradiated polymers became insoluble and no longer exhibited a T_g below decomposition temperature. The crosslinked triazene containing polyesters show strong absorption at λ = 308 nm and are therefore interesting candidates for applications using XeCl excimer laser ablation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1903–1910, 2000     

Synthesis of asymmetric iron-pybox complexes and their application to aziridine forming reactions

The synthesis of a series of iron-pybox complexes and their employment in the catalytic asymmetric aziridine forming reaction is presented. When AgSbF₆ is used as an initiator, the i-pr- and t-bu-pybox complexes produce 47% of the cis-aziridine in moderate ee’s with the bulk of side products consisting of the trans-isomer and β-amino-α,β-unsaturated esters (AUE’s).     

Synthesis and reactivity of 3-(2-chloroalkyl)-2,2-dihaloaziridines

3-(2-Chloroalkyl)-2,2-dihaloaziridines were synthesized via cycloaddition of dihalocarbenes to the CN double bond of β-chloroimines. Under the action of Lewis acids or HCl, N-C³ bond cleavage occurred, giving rise to N-substituted 2,4-dichloro-3,3-dimethylbutanamides, which were further converted to 3-chloropyrrolidin-2-ones under alkaline conditions. When 2,2-dichloro-3-(2-chloro-1,1-dimethylethyl)-1-phenylaziridine was reacted with sodium methoxide, aziridine ring opening with N-C² bond cleavage took place, leading to methyl 4-chloro-3,3-dimethyl-2-(phenylamino)butanoate.     

Synthesis and reactivity of non-activated 2-(chloromethyl)aziridines

An efficient synthesis of non-activated 2-(chloromethyl)aziridines and 2-chloromethyl-2-methylaziridines as new representatives of the class of 2-(halomethyl)aziridines was developed. Furthermore, the reactivity of these azaheterocycles was assessed and compared to that of their brominated counterparts, pointing to a similar profile for 2-(chloromethyl)aziridines and 2-(bromomethyl)aziridines on the one hand, and a different behaviour of 2-chloromethyl-2-methylaziridines versus 2-bromomethyl-2-methylaziridines concerning their aptitude towards ring expansion to azetidines on the other hand.     

Synthesis and 13C NMR features of N-substituted aziridino[60]fullerenes

Russian Chemical Bulletin - An effective cycloaddition of organic azides to fullerene C60 in the presence stoichiometric amounts of Cu(OTf)2 to form individual aziridino[60]fullerenes was...     

Synthesis of 9-Alkyl- and 9-Arylthiophenanthrenes

A simple method for the preparation of 9-alkyl- and 9-arylthio-phenanthrenes from 9-bromophenanthrene and a thiol is described.