Regioselective ring opening of 2-methylaziridine derivatives with F- and F-fluoride

Regioselectivity of the nucleophilic ring opening of N-benzoyl (Bz) and N-benzyloxycarbonyl (Cbz) activated 2-methylaziridines with anhydrous tetramethylammonium fluoride, anhydrous hydrogen fluoride, and ¹⁹F or [¹⁸F]-labelled potassium cryptand fluoride ([K₂₂₂][^18/19F]) were investigated. Whereas all reactions with rigorously anhydrous N(CH₃)₄F did not ring-open the aziridines, reactions with anhydrous HF exclusively yielded the 2-fluoropropanamine derivatives. Reactions of Bz-protected and Cbz-protected 2-methylaziridine with [K₂₂₂][^18/19F] yielded the 2-fluoropropanamine and 1-fluoro-2-propanamine derivatives as the major products, respectively, and represents the first example of regiocontrol during ring opening of aziridines with [¹⁸F]-fluoride.     

The reductive ring opening of some derivatives of isatin

Treatment of two isatin-3-imines, 3-isopropyIamino-1-methylindoline-2-one and 3-cyclohexylamino-1-methylindolin-2-one with sodium borohydride produced the fully-reduced anilines 2-isopropylamino-2-(2-methylaminophenyl) ethanol and 2-cyclohexylamino-2-(2-methylaminophenyl) ethanol, respectively. Reductive ring-opening of derivatives of isatin is not observed in related examples when either catalytic or lithium aluminum hydride reduction are employed and it is concluded that the present effect is dependant upon the softness of sodium borohydride as a reducing agent.     

Living ring opening metathesis polymerization of mesogenic norbornene derivatives

A new class of SCLCPs was prepared by polymerizing mesogenic norbornene derivatives using Mo(CHCMe₂R)(N-2,6-C₆H₃-i-Pr₂)(O-t-Bu)₂ (R = CH₃ or Ph). Monomers based on norbornene ring systems were chosen because the rings are highly strained and therefore yield irreversible polymerizations. The Mo-alkylidene initiators were chosen because they initiate norbornene derivatives relatively fast and quantitatively, and provide stable chain ends which have low reactivity to both the internal double bonds of the polymer backbone and the functional groups present in the monomers. The apparent absence of termination and transfer reactions in ROMP results in polymerizations which appear to be living, and the fast initiation and irreversible chain growth leads to polymers with narrow molecular weight distributions in which the degree of polymerization is controlled by the ratio of monomer to initiator used. The resulting well-defined polymers were used to determine the most basic structure-property relationships of this new class of SCLCPs. The thermotropic behavior of both terminally attached and laterally attached SCLCPs based on polynorbornene backbones becomes independent of molecular weight at approximately 25 repeat units. In addition, polydispersity was found to have no effect on the breadth of nematic phase transitions in the terminally attached polymers, with the transition temperature determined simply by the number average degree of polymerization.     

Trimethylchlorosilane induced ring opening of 2-alkyloxazolidines to enamine derivatives

2-Alkyloxazolidines (5) were ring-opened by trimethylchlorosilane with N,N-diisopropylamine to give N-[2-(trimethylsilyloxy)alkyll-enamines (6). A MgCl₂ promoted Michael reaction of chiral enamines thus prepared was achieved with asymmetric induction.     

Electrochemical aging of poly(aniline) and its ring substituted derivatives

Aniline and methyl, ethyl, propyl, and methoxy ring substituted derivatives have been polymerized by electrochemical methods. The reduction of the film produces aging of the polymers. This is followed by the changes in the current/potential profile of the voltammetric response. The effect of the substituents produces changes in both the extent and the rate of aging. The rate of aging can be represented by a Roginsky-Zeldovich or Elovich type of kinetics characterized by a pseudo zero order rate constant and a self-inhibiting parameter. Both parameters and the extent of aging are related to the free volume available for the different types of polymers.     

Acetylenic derivatives of aniline

Conclusions The direct condensation of iodoanilines with 2-methyl-3-bu1yn-2-ol gave acetylenic carbinols, whose cleavage by the reverse Favorskii reaction leads to ethynylanilines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1184–1186, May, 1982.     

Synthesis of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of N-substituted-2(3H)-benzothiazolones

The decarbalkoxylations of disubstituted geminal diesters by water–DMSO with added salts (KCN or NaCN) is a convenient preparative route leading to the corresponding monoesters. Herein, we described an efficient and very simple methodology for the preparation of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of the corresponding N-substituted-2(3H)-benzothiazolones in the presence of disubstituted geminal diester, KCN, and water–DMSO.     

Enantioselective hydroformylation of aniline derivatives

We have developed a ligand that reversibly binds to aniline substrates, allowing for the control of regioselectivity and enantioselectivity in hydroformylation. In this paper we address how the electronics of the aniline ring affect both the binding of the substrate to the ligand and the enantioselectivity in this reaction.     

Overtone spectra of aniline derivatives

Overtone spectra of 2-ethylaniline, N-methylaniline, N-ethylaniline, N,N-dimethylaniline and N,N-diethylaniline have been studied in 2500-15000 cm(-1) region. Vibrational frequency and anharmonicity constants for aryl/alkyl C-H stretch and N-H stretch vibrations have been determined. The effect of substitution of C(2)H(5) group on the ortho position in the ring and CH(3)/C(2)H(5) at the positions of the H-atom in NH(2) group has been studied in these molecules. It is noted that the aryl C-H stretching frequency and the N-H stretching frequency is appreciably increased due to the replacement of H in NH(2) group by CH(3)/C(2)H(5). These experimental observations are well supported by theoretical calculations for charge density on N-atom using molecular orbital AM(1) method.     

PXPd-catalyzed borylation of aniline derivatives

Addition of pinacolborane (HBO₂C₂Me₄) to 2-iodoaniline can be catalyzed using a number of palladium complexes, including [(t-Bu)₂PCl]₂PdCl₂ (PXPd), to give the corresponding boronate ester 2-H₂NC₆H₄(BO₂C₂Me₄) in excellent yields. The PXPd system could also be used in the catalyzed borylation of substituted anilines to give the corresponding aminoboronate esters in moderate to high yields.      

Hydrolytic opening of the quinazoline ring in 3-furfuryl-4-oxo-3,4-dihydroquinazoline derivatives

Ethyl 3-furfuryl-4-oxo-3,4-dihydroquinazoline-2-carboxylate extremely readily undergoes hydrolysis in acid, alkaline, or neutral medium with formation of 2-(2-ethoxy-1,2-dioxoethylamino)-N-furfurylbenzamide. The reaction of ethyl 3-furfuryl-4-oxo-3,4-dihydroquinazoline-2-carboxylate with phenylmagnesium bromide yields N-furfuryl-2-(2-hydroxy-2,2-diphenyl-1-oxoethylamino)benzamide as a result of hydrolytic cleavage of the quinazoline ring.     

Chemoselective ring opening of benzoxazaphosphinines

Cyclization of 2-[(4-chloroanilino)methyl]phenol (1) with thiophosphoryl chloride afforded 2-chloro-3-(4-chlorophenyl)-3,4-dihydro-2H-1,3,2λ⁵-benzoxazaphosphinine-2-thione (2). Reaction of 2 with various heterocyclic amines (3) in the presence of Et₃N/NaH gave 3-(4-chlorophenyl)-2-nitrogen heterocyclic substituted-3,4-dihydro-2H-1,3,2λ⁵-benzoxaza-phosphinine-2-thiones (4). Further reaction of 4 with the N-sodium salt of amino heterocyclics in the presence of HCl at 50-60 °C opened the benzoxazaphosphinine ring chemoselectively at the endocyclic P-O bond and yielded 2-[4-chloro(heterocyclic substituted-phosphorothioyl)anilino]methylphenols 5-13.     

Palladium-mediated ring opening of hydroxycyclopropanes

[reaction: see text] The palladium-mediated ring opening of substituted cyclopropanols has been found to take place predominantly at the less substituted C-C bond. Thus, sequential application of the titanium-mediated cyclopropanation of esters and the palladium-mediated ring opening of the resulting cyclopropanols provides a convenient method for functionalizing monosubstituted olefins.     

Rearrangements initiated by trimethylsilyl iodide: the facile ring opening of some cyclobutanone derivatives

The powerful electrophile trimethylsilyl iodide in the presence of certain catalysts rapidly and cleanly initiates the ring opening of a variety of cyclobutanone derivatives in a highly regioselective fashion yielding ultimately β-iodoketones.     

Regioselective ring opening of the chiral non-racemic furoindolizidinols. New entry to alkylindolizidinediol derivatives

New homochiral 6-ethyl-7,8-indolizidinediol derivatives, related to the bioactive dihydroxylated indolizidine alkaloids, are reported to be easily accessible in four or five steps from enantiopure 9-hydroxy-octahydrofuro[3,2-f]indolizin-6(2H)-ones in good overall yields and high diastereomeric purities. The simple procedure used herein involves a regiospecific THF-ring opening as a key step, in addition to the C–Br linkage reduction, and the alcohol deprotection followed by lactam reduction.     

Photochemical ring opening of barbital

Photolysis of barbital yields derivatives of urea and biuret. The mechanism of ring opening involves an isocyanate intermediate.