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1.
J Org Chem ; 89(9): 6533-6538, 2024 May 03.
Article in English | MEDLINE | ID: mdl-38607996

ABSTRACT

Treatment of mixed phosphonium-iodonium ylides featuring a six-membered phenoxaphosphonium fragment with aqueous tetrafluoroboronic acid induces a rearrangement, resulting in expansion of the phosphacycle and oxidation of the phosphorus atom. The target difficult-to-access dibenzo[b,f][1,4]oxaphosphepine oxides (3 examples) were isolated in excellent yields (up to 95%) as mixtures of stereoisomers. Hydrolysis of a five-membered mixed ylide, a dibenzophosphole derivative, predominantly preserves the phosphole system with cycle expansion occurring as a side process.

2.
Org Biomol Chem ; 20(39): 7795-7802, 2022 10 12.
Article in English | MEDLINE | ID: mdl-36148530

ABSTRACT

Lewis acid-catalysed reactions of donor-acceptor cyclopropanes with 1,3-disubstituted 5-aminopyrazoles were investigated. Under catalysis with gallium(III) chloride, products of the three-membered ring opening via a nucleophilic attack of the exocyclic amino group were obtained in a chemoselective manner. Oppositely, in the presence of scandium(III) triflate, products of either N-alkylation or C(4)-alkylation, or a mixture of both were formed. The products of the C(4) alkylation were transformed in one step into tetrahydropyrazolo[3,4-b]azepines that are attractive for medicinal chemistry and pharmacology.


Subject(s)
Cyclopropanes , Gallium , Azepines , Chlorides , Lewis Acids , Molecular Structure , Pyrazoles , Scandium
3.
J Am Chem Soc ; 143(34): 13952-13961, 2021 09 01.
Article in English | MEDLINE | ID: mdl-34406759

ABSTRACT

The importance of intramolecular constraints in cyclic transition-state geometries is especially pronounced in n-endo-tet cyclizations, where the usual backside approach of a nucleophile to the breaking bond is impossible for the rings containing less than eight atoms. Herein, we expand the limits of endo-tet cyclizations and show that donor-acceptor cyclopropanes can provide a seven-membered ring via a genuine 6-endo-tet process. Substrates containing a N-alkyl-N-arylcarbamoyl moiety as an acceptor group undergo Lewis acid-induced cyclization to form tetrahydrobenz[b]azepin-2-ones in high yields. The reaction proceeds with the inversion of the configuration at the electrophilic carbon. In this process, a formally six-membered transition state yields a seven-membered ring as the pre-existing cycle is merged into the forming ring. The stereochemistry of the products can be controlled by the reaction time and by the nature of Lewis acid, opening access to both diastereomers by tuning of the reaction conditions.

4.
Polymers (Basel) ; 13(15)2021 Aug 01.
Article in English | MEDLINE | ID: mdl-34372172

ABSTRACT

It was found that sulfanylethanoic and 3-sulfanylpropanoic acids are effective regulators of molecular weight with chain transfer constants of 0.441 and 0.317, respectively, and show an unexpected acceleration effect on the radical polymerization of N-vinyl-2-pyrrolidone, initiated by 2,2'-azobisisobutyronitrile. It was determined for the first time that the thiolate anions of mercapto acids form a high-temperature redox initiating system with 2,2'-azobisisobutyronitrile during the radical polymerization of N-vinyl-2-pyrrolidone in 1,4-dioxane. Considering the peculiarities of initiation, a kinetic model of the polymerization of N-vinyl-2-pyrrolidone is proposed, and it is shown that the theoretical orders of the reaction rate, with respect to the monomer, initiator, and chain transfer agent, are 1, 0.75, 0.25, and are close to their experimentally determined values. Carboxyl-containing techelics of N-vinyl-2-pyrrolidone were synthesized so that it can slow down the release of the anticancer drug, doxorubicin, from aqueous solutions, which can find its application in the pharmacological field.

5.
J Org Chem ; 86(17): 12300-12308, 2021 09 03.
Article in English | MEDLINE | ID: mdl-34382810

ABSTRACT

A scandium trifluoromethanesulfonate-catalyzed reaction of donor-acceptor cyclopropanes with 6-amino-1,3-dimethyluracil was found to proceed as three-membered ring opening via nucleophilic attack of the C(5) atom of an ambident nucleophile serving as an enamine equivalent. It was shown that, under basic conditions, the obtained products underwent cyclization to 6,7-dihydro-1H-pyrimido[4,5-b]azepine-2,4,8-triones, an interesting subclass of nucleobase analogues.


Subject(s)
Azepines , Cyclopropanes , Cyclization , Uracil/analogs & derivatives
6.
Angew Chem Int Ed Engl ; 60(14): 7927-7934, 2021 Mar 29.
Article in English | MEDLINE | ID: mdl-33433034

ABSTRACT

We propose a new concept of the triple role of protic ionic liquids with nucleophilic anions: a) a regenerable solvent, b) a Brønsted acid inducing diverse transformations via general acid catalysis, and c) a source of a nucleophile. The efficiency of this strategy was demonstrated using thiocyanate-based protic ionic liquids for the ring-opening of donor-acceptor cyclopropanes. A wide variety of activated cyclopropanes were found to react with 1-methylimidazolium thiocyanate under mild metal-free conditions via unusual nitrogen attack of the ambident thiocyanate ion on the electrophilic center of the three-membered ring affording pyrrolidine-2-thiones bearing donor and acceptor substituents at the C(5) and C(3) atoms, respectively, in a single time-efficient step. The ability of 1-methylimidazolium thiocyanate to serve as a triplex reagent was exemplarily illustrated by (4+2)-annulation with 1-acyl-2-(2-hydroxyphenyl)cyclopropane, epoxide ring-opening and other organic transformations.

7.
Molecules ; 25(23)2020 Dec 05.
Article in English | MEDLINE | ID: mdl-33291488

ABSTRACT

A simple general method for the synthesis of 1-acyl-2-(ortho-hydroxyaryl)cyclopropanes, which belong to the donor-acceptor cyclopropane family, has been developed. This method, based on the Corey-Chaykovsky cyclopropanation of 2-hydroxychalcones, allows for the preparation of a large diversity of hydroxy-substituted cyclopropanes, which can serve as promising building blocks for the synthesis of various bioactive compounds.


Subject(s)
Cyclopropanes/chemistry , Ketones/chemistry , Biological Factors/chemistry
8.
J Org Chem ; 85(2): 1146-1157, 2020 01 17.
Article in English | MEDLINE | ID: mdl-31804074

ABSTRACT

A straightforward method for ring opening of donor-acceptor cyclopropanes with trimethylsilyl cyanide as a surrogate of cyanide ion in the presence of B(C6F5)3 or trifluoromethanesulfonic acid as a catalyst has been developed. The methodology provides a short route to γ-cyanoesters that can be useful synthetic intermediates for the synthesis of diverse bioactive molecules such as glutaric and δ-aminovaleric acid derivatives, 3-arylpiperidines, or other substituted phenethylamines. Oppositely, the attempts to synthesize these γ-cyanoesters by direct reaction of cyclopropanes with sodium cyanide under typical SN2 conditions led to the formation of 2-arylsuccinonitriles.

9.
RSC Adv ; 9(45): 26219-26223, 2019 Aug 19.
Article in English | MEDLINE | ID: mdl-35531024

ABSTRACT

In situ acquisition of the reaction between benzoyl phosphonium-iodonium ylide and p-methoxyphenylacetylene in an NMR spectrometer reveals the CIDNP effect in 31P and 1H NMR spectra of major products, substituted furan (emission) and phosphonium salt (enhanced absorption). The mechanism of products formation via radical pairs is discussed.

10.
Molecules ; 24(1)2018 Dec 24.
Article in English | MEDLINE | ID: mdl-30586901

ABSTRACT

A simple method has been developed for the synthesis of cyclopropa[c]coumarins, which belong to the donor-acceptor cyclopropane family and, therefore, are promising substrates for the preparation of chromene-based fine chemicals. The method, based on the acetic acid-induced intramolecular transesterification of 2-arylcyclopropane-1,1-dicarboxylates, was found to be efficient for substrates containing hydroxy group directly attached to the aromatic ring.


Subject(s)
Carboxylic Acids/chemical synthesis , Coumarins/chemical synthesis , Cyclopropanes/chemical synthesis , Carboxylic Acids/chemistry , Coumarins/chemistry , Cyclopropanes/chemistry , Esterification
11.
J Org Chem ; 83(2): 543-560, 2018 01 19.
Article in English | MEDLINE | ID: mdl-29110480

ABSTRACT

We report a mild Lewis acid induced isomerization of donor-acceptor cyclopropanes, containing an alkenyl moiety and diverse electron-withdrawing group(s) at the adjacent positions, into substituted cyclopentenes. We have found that 1,1,2-trisubstituted cyclopent-3-enes were exclusively obtained in yield of 51-99% when cyclopropanes with a 2-substituted alkenyl group as a donor underwent isomerization. For cyclopropanes bearing a trisubstituted alkenyl group either the corresponding cyclopent-3-enes or isomeric cyclopent-2-enes having two acceptor groups at the C(1) atom were formed, with the reaction selectivity being determined by the applied Lewis acid. We have shown that the reactivity of the donor-acceptor cyclopropane increases with the increase of the electron-donating character of (hetero)aromatic group attached to the alkenyl moiety. The synthetic utility of the developed methodology was also demonstrated through the synthesis of polysubstituted cyclopentane and piperidine derivatives.

12.
Photochem Photobiol Sci ; 15(12): 1558-1566, 2016 Nov 30.
Article in English | MEDLINE | ID: mdl-27858050

ABSTRACT

Novel hetarylazo dyes containing tetrazole and tetra- or dihydroquinoline moieties were synthesized and their spectral properties in solvents of different polarities and H-bonding abilities were examined. The dyes exhibit solvatochromism dramatically depending on the proton accepting ability of solvents: (DMSO > H2O > MeOH > ACN > CH2Cl2) and the dye concentration. Upon dilution the absorption maximum of the visible band shows a blue shift and the absorption coefficient of the maximum decreases. This was accounted for by complex formation either between the dye molecules or between the dye and solvent molecules. The H-bond with partial proton transfer is formed between the acidic NH group of the tetrazole moiety of a dye molecule and the basic NH group of the hydroquinoline moiety of the other dye molecule or with a solvent with proton accepting ability. Upon dilution the equilibrium shifts to the complex with a solvent. The coexistence of several forms of the dye molecules with different absorption spectra was demonstrated in pulse photolysis upon excitation by light with different wavelengths. Three forms of cis-isomers were registered. The photogenerated cis-isomers decay with lifetimes from 200 µs to 5 ms. The fast cis-trans dark isomerization determines the photostability of the dyes.


Subject(s)
Coloring Agents/chemistry , Photochemistry , Quinolines/chemistry , Tetrazoles/chemistry , Isomerism , Solvents
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