Cyclopropanation of areno-condensed 4 H -pyrans with dihalocarbenes
- PDF / 310,516 Bytes
- 6 Pages / 594 x 792 pts Page_size
- 68 Downloads / 135 Views
Cyclopropanation of areno-condensed 4H-pyrans with dihalocarbenes Irina А. Semenova1, Vitaly А. Osyanin1*, Maxim R. Demidov1, Dmitry V. Osipov1, Yuri N. Klimochkin1 1
Samara State Technical University, 244 Molodogvardeyskaya St., Samara 443100, Russia; е-mail: [email protected] Submitted September 28, 2020 Accepted October 26, 2020
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(11), 1417–1422
The addition of dihalocarbenes to 1H-benzo[f]chromenes and 4H-chromenes gave a number of dihalotetrahydro(benzo)cyclopropa[b]chromenes containing donor and acceptor substituents at different positions. It was found that in the case of 1,3-disubstituted 1H-benzo[f]chromenes, the reaction proceeds diastereoselectively with the formation of trans-isomers. 12H,13H-7a,12a-Methanobenzo[f]indeno[1,2-b]chromene and 12,13-dihydro-14H-7a,13a-methanodibenzo[a,h]xanthene, representatives of new heterocyclic systems, were obtained. Keywords: 1H-benzo[f]chromenes, dihalocarbenes, gem-dihalocyclopropanes, tetrahydrocyclo(benzo)propa[b]chromenes, [2+1] cycloaddition.
Geminal dihalocyclopropanes annulated with a dihydroor tetrahydropyran fragment are valuable intermediates in organic synthesis due to the possibility of substitution of halogen atoms with various functional groups and easy opening of the strained three-membered ring.1 In this case, further transformations can be accompanied by both expansion of the six-membered heterocycle or its contraction or retention. In the presence of nucleophiles and Ag(I) salts or bases2 as well as during thermolysis,3 the formation of oxepine derivatives or hydrogenated β-(halomethylene)pyrans is often observed.2a,d In this case, the addition of nucleophiles, as a rule, proceeds regioselectively at the α-position relative to the endocyclic oxygen atom due to its stabilizing effect on cationic intermediates. In some cases, tetrahydrofuran derivatives were isolated (Scheme 1).4 Usually, gem-dichlorocyclopropanation of 3,4-dihydro2H-pyrans is carried out under the conditions of phasetransfer catalysis by the action of CHCl3 and alkali,2e,5 with sonochemical activation in the presence of Mg and CCl4,6 or by the action of dichlorocarbene generated under anhydrous conditions from Cl3CCO2Et and alcoholates.7 In this respect, the annulation of the cyclopropane moiety to areno-condensed pyrans has been much less studied.7b,8 In particular, only one example of the preparation of the 0009-3122/20/56(11)-1417©2020 Springer Science+Business Media, LLC
Scheme 1
heterocyclic system of benzo[f]cyclopropa[b]chromene from the corresponding benzochromone has been described in the literature.9 At the same time, the chromane fragment is key in the structure of many natural flavonoids and biologically active substances,10 while cyclopropa[b]chromenes were found to be antagonists of glutamate receptors 111 and an inhibitor of HIV-1 replication 2,12 a derivative of calanolide A (Fig. 1). In addition, we have previously discovered that some benzo-fused pyrans are α-glucosidase inhibitors, which may be effe
Data Loading...
