Ring opening of 2-(bromomethyl)-1-sulfonylaziridines towards 1,3-heteroatom substituted 2-aminopropane derivatives

1,3-Heteroatom substituted 2-aminopropane derivatives have been prepared from 2-(bromomethyl)-1-sulfonylaziridines for the first time using sodium azide or different potassium phenoxides in water in the presence of silica gel. The applicability of 1-arenesulfonyl-2-(bromomethyl)aziridines for the synthesis of functionalized sulfonamides has also been demonstrated towards different 1,3-dialkoxy-2-(tosylamino)propanes and 1,3-dialkylthio-2-(tosylamino)propanes upon treatment with the appropriate sodium alkoxide or sodium alkylthiolate in the corresponding alcohol or in methanol, respectively.     

Ring opening reactions of 1-arenesulfonyl-2-(bromomethyl)aziridines

The reactivity of 1-arenesulfonyl-2-(bromomethyl)aziridines with respect to lithium dialkylcyanocuprates and lithium dialkylcuprates (Gilman reagents) has been evaluated for the first time, pointing to the conclusion that these substrates can be applied successfully as synthetic equivalents for the 2-aminopropane dication synthon towards 2-alkylaziridines and α-branched N-tosylamides in good yields.     

Synthesis of quaternary allylammonium salts via ring opening of 1-benzyl-2-(bromomethyl)aziridines

Treatment of 1-benzyl-2-(bromomethyl)aziridine, and some aryl substituted analogues, with an excess of iodomethane resulted in N-allyl-N-benzyl-N,N-dimethylammonium salts, in good yields. These quaternary allylammonium salts are of importance in different fields, from organic synthesis and polymeric chemistry to agricultural use.     

A novel synthesis of 3-aminoazetidines by ring transformation of 2-(bromomethyl)aziridines

A one-step approach to the biologically interesting 3-aminoazetidines is described. The reaction concerns a ring transformation of 1-arylsulfonyl-2-(halomethyl)aziridines with aliphatic amines under various reaction conditions.     

Synthesis of naproxen via regioselective ring opening of (2S,3S)-epoxy-1-butanol

(S)-Naproxen was synthesized by the regioselective and stereospecific epoxide ring opening of (2S,3S)-epoxy-1-butanol (2) with diethyl-2-(6-methoxynaphthyl)aluminium (5) as the key step. Thus, treatment of di-ethylaluminate of 2 with 5 at 0° afforded (2S,3S)-3-(6-methoxy-2-naphthyl)butan-1,2-diol (6) , which was oxidized by sequential treatment with sodium periodate and potassium permanganate in a mixture of tert-butyl-alcohol and phosphate buffer (pH 7.0) to give naproxen in high enantiomeric purity.     

A new method for regioselective synthesis of 2-substituted 1-(methoxycarbonyl)-1,2-dihydropyridines

2-Substituted 1,2-dihydropyridines including an optically active one were regioselectively prepared from 2-substituted piperidines through three intermediates, that is, (a) 1,2,3,4-tetrahydropyridines, (b) 5-bromo-6-methoxypiperidines, and (c) 1,2,3,6-tetrahydro- 6-methoxypyridines.     

Diels–Alder reactivity of 2-(bromomethyl)-1,4-quinone and 2-bromo-5-(bromomethyl)-1,4-quinone with cyclopentadiene and the synthesis of new substituted pentacyclic systems

Photochemical synthesis of the novel compounds 3-bromotetracyclo [5.3.1.0^2,6.0^4,8] undec-10(12)-ene-9,11-dione, 1-(bromomethyl)pentacyclo [5.4.0.0^2,6.0^3,10.0^5,9]undeca-8,11-dione and 1-bromo-9-(bromomethyl)pentacyclo [5.4.0.0^2,6.0^3,10.0^5,9]undeca-8,11-dione is described.     

An efficient synthesis of 2-(guaiazulen-1-yl)furan derivatives via intramolecular Wittig reactions

An efficient and mild synthesis of 2-(guaiazulen-1-yl)furans,starting from easily accessible 1-(3-aryl-2-cyanopropenoyl) guaiazulenes,tributylphosphine and acyl chlorides,is described.The strategy employs the intramolecular Wittig protocol as a key step to append the crticial furan ring,leading to the highly functional furans in good yields.     

A new synthesis of macrocyclic keto-lactones via ring expansion of 2-(3-hydroxypropyl)-2-nitrocycloalkanones

2-(3-Hydroxypropyl0-2-nitrocycloalkanones undergo base-catalysed isomerisation into nitro-lactones containing four more atoms in the ring, which can be smoothly converted to the corresponding keto-lactones.     

A regioselective synthesis of aryl substituted arylacetates through ring transformation by ethyl levulinate

A regioselective synthesis of sterically hindered ethyl arylacetates in one step through ring transformation of suitably functionalized 6-aryl-3,4-disubstituted-2H-pyran-2-ones with ethyl levulinate at room temperature in excellent yields is described.     

Highly regioselective synthesis of 1,3-diiodonaphthalene derivatives via a sequential cascade iodocyclization

A novel and flexible sequentially cascade iodocyclization for the synthesis of highly substituted 1,3-diiodinated naphthalene derivatives in up to 99% yield under mild conditions is reported. The dihalogenated moiety can be readily introduced into the naphthalenes in a position that is usually not easily functionalized.     

A new synthesis of substituted 2(1H)-pyrazinones

The hydrohalides of 2-sec-aminoalkanenitriles on treatment with oxalyl halides in o-dichlorobenzene at 80-100° give 3, 5-dihalo-2(1H)-pyrazinones, of which the 3-halo substituent is easily replaced by nucleophiles. A reaction mechanism for the pyrazinone synthesis is proposed.     

Asymmetric synthesis of 2-(2-pyridyl)aziridines from 2-pyridineimines bearing stereogenic N-alkyl substituents and regioselective opening of the aziridine ring

The addition of chloromethyllithium to the imine derived from 2-pyridinecarboxaldehyde and (S)-valinol, protected as its O-trimethylsilyl ether, gave the 1,2-disubstituted aziridine with good yield and diastereoselectivity. The analogous reaction performed on the imine derived from (S)-valine methyl ester gave the product containing the aziridine ring and the alpha-chloro ketone group coming from the attack of chloromethyllithium to the ester function. Other stereogenic alkyl substituents at nitrogen gave less satisfactory results. Moreover, the aziridination protocol did not work on other aromatic imines which were not capable of bidentate chelation, e.g., 3- and 4-pyridineimine and benzaldimine. Preliminary studies showed the possibility to carry out regio- and stereospecific opening reactions of 2-(2-pyridyl)aziridines by attack of internally generated or external nucleophiles.     

Facile isocyanide-based one-pot three-component regioselective synthesis of highly substituted pyridin-2(1H)-one derivatives at ambient temperature

A novel one-pot three-component regioselective synthesis of highly substituted pyridin-2-one derivatives starting from simple and readily available starting materials is described. The reactive zwitterionic intermediate generated by the addition of an isocyanide to dimethyl acetylenedicarboxylate (DMAD) was trapped with N-arylidene-2-cyanoacetohydrazides to afford the title compounds in moderate to good yields at room temperature without using any catalyst and other additives.     

Methodology for regioselective synthesis of substituted pyridines via intramolecular oximino malonate hetero Diels-Alder reactions

[structure] Various substituted pyridines can be prepared regioselectively by a sequence involving an intramolecular thermal or high-pressure Diels-Alder cycloaddition of an oximino malonate dienophile tethered to a dienic carboxylic acid, followed by mild aromatization of the resulting cycloadduct with cesium carbonate in DMF at room temperature.     

A new halopropargylation of alkynes promoted by boron trihalides. highly stereo- and regioselective syntheses of substituted (Z)-1-halo-1,4-enyne derivatives

[reaction: see text] A new halopropargylation of alkynes promoted by boron trihalides has been developed. Reactions of (Z)-2-halo-1-vinylboron dihalides (generated in situ via reaction of alkynes with boron trihalides) with lithium propargyloxides in CH(2)Cl(2) at room temperature produce the corresponding (Z)-1-halo-1,4-enynes in modest to good yields.     

Stereospecific isomerization of 2-(1-bromoalkyl)-1-sulfonylaziridines using magnesium bromide

Novel stereospecific isomerization of 2-(1-bromoalkyl)-1-sulfonylaziridines into 2-(bromomethyl)-3-alkyl-1-sulfonylaziridines using magnesium bromide is described. The suitable choice of solvent led to good yields and diastereoselectivites.     

Cyclopropanation and carbonyl olefination utilizing 2-(Alk-1-yn-1-yl)-2-(trialkylsilyl)-1,3-dithianes via regioselective generation of titanium alkynylcarbene complexes

Cp(2)Ti[P(OEt)(3)](2)-promoted reactions of 2-(alk-1-yn-1-yl)-2-(trialkylsilyl)-1,3-dithianes (RS)(2)C(Si)CCR with terminal olefins and carbonyl compounds produced (trialkylsilylethynyl)cyclopropanes and 1-(trialkylsilyl)alk-3-en-1-ynes, respectively. These compounds were suggest to be produced via the formation of intermediary titanium alpha-(trialkylsilylethynyl)carbene complexes Cp(2)Ti=C(R)CCSi in preference to their regioisomers, alpha-(trialkylsilyl)alkynylcarbene complexes Cp(2)Ti=C(Si)CCR.     

Preparation and cycloaddition reactions of enantiopure 2-(N-acylamino)-1,3-dienes for the synthesis of octahydroquinoline derivatives

Stille, Suzuki-Miyaura, and Sonogashira cross-coupling reactions were carried out with a glutarimide-derived vinyl phosphate, bearing a chiral auxiliary on the N atom, to prepare enantiopure 2-(N-acylamino)-1,3-dienes as partners in Diels-Alder reactions. The cycloadditions were performed with various dienophiles under thermal conditions, with or without Lewis acids. With maleimides, the preferential formation of endo cycloadducts was observed, whereas with acrylamides the exo approach prevailed. Furthermore, in the latter case, 6-substitued octahydroquinolinones were obtained in accordance with the predicted regioselectivity. Since diastereopure compounds were in all cases obtained either by chromatography or by crystallization, and because of the easy access to a variety of boronic acids, to be used in the coupling step, this methodology is useful for the short synthesis of differently substituted, enantiopure octahydroquinolinones amenable to further transformation into decahydroquinolines possessing interesting biological activities.