Alkynylhalocarbenes

(Alk-1-ynyl)chlorocarbenes (3), generated from 1,1-dihaloalk-2-ynes and 3-substituted 3-bromo-1,1,1-trichloropropanes under the action of Bu^tOK in THF at 20°C, react with excess alkali metal alkoxide4 to give 3-substituted 2-(alk-1-ynyl)oxiranes (6) in 26–78% yields, most likely as a result of insertion of carbene3 into the α-C−H bond of alkoxides4 and subsequent cyclization of the resulting 1-substituted 2-chloro-2-(alk-1-ynyl)etoxides. The yields of oxiranes6 depend on the nature of the alkali metal used to prepare alkoxides4 and on the method employed for the preparation of the latter. For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1185–1192, June, 1998.     

Reaction of 1-(alk-1-ynyl)-1-halocyclopropanes with alcohols and phenol in KOH/DMSO as a method for the synthesis of 2-alkoxy-1-alkynyl- and 1-alkynyl-2-phenoxycyclopropanes

The reaction of 1-(alk-1-ynyl)-1-halocyclopropanes with alcohols or phenol in KOH/DMSO at 80–100 °C leads to the corresponding alkynylalkoxy- and alkynylphenoxycyclopropanes in up to 80% yield. These reactions proceed through the intermediate formation of conjugated alkynylcyclopropenes capable of the in situ addition of alcohols at the double bond of the cyclopropene fragment. Regio- and stereoselectivity of the process is defined by the nature of substituents in the starting cyclopropanes and the structure of alcohols used.     

On the possible enhancement of the magnetic field by neutrino reemission processes in the mantle of a supernova

Urca neutrino reemission processes under the conditions in the mantle of a supernova with a strong toroidal magnetic field are investigated. It is shown that P-parity violation in these processes can be manifested macroscopically as a torque that rapidly spins up the region of the mantle occupied by such a field. Neutrino spin-up of the mantle can strongly affect the mechanism of further generation of the toroidal field, specifically, it can enhance the field in a small neighborhood of the rigid-body-rotating core of the progenitor star. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 5, 337–342 (10 March 1999)     

Alkynylhalocarbenes. 4. Generation of (alk-1-ynyl)halocarbenes from 3-substituted 1,1,1,3-tetrahalopropanes under the action of bases

When treated with KOH under phase-transfer catalysis or with Bu^tOK, 3-substituted (alkyl or phenyl) 1,1,3-tribromo-1-fluoropropanes 1a—c exclusively generate previously unknown (alk-1-ynyl)fluorocarbenes 5a—c, which react with olefins to give 1-(alk-1-ynyl)-1-fluorocyclopropanes 6a—h in 12—69% yields. Under analogous conditions, 3-alkyl- and 3-aryl-3-bromo-1,1,1-trichloropropanes 2a—c selectively afford (alk-1-ynyl)chlorocarbenes 7a—c, which are trapped by olefins to form the corresponding 1-(alk-1-ynyl)-1-chlorocyclopropanes 8a—k in 35—70% yields. (Phenylethynyl)chlorocarbene 7a is also selectively generated from 1,1,1,3-tetrachloro-3-phenylpropane (3a) upon its treatment with Bu^tOK. With an excess of 2,3-dimethylbut-2-ene or 2-methylpropene, carbene 7a yields 1-chloro-1-(phenylethynyl)cyclopropanes 8a or 8c, respectively. In contrast, 1,1,1,3-tetrachloroheptane 3b and 3-alkyl- and 3-phenyl-1,1,1,3-tetrabromopropanes 4a,c,f react with bases in the presence of olefins to give, along with the corresponding 1-(alk-1-ynyl)-1-halocyclopropanes 8a,c,d and 11a—f, vinylidenecyclopropanes 12a,c—g, which suggests the generation, under these conditions, both (alk-1-ynyl)halocarbenes 7b and 9a—c and vinylidenecarbenes 10 and 11a—c. The composition and structures of intermediate products in the reactions of tetrahalides 1b, 2a, 2b, 3a, and 3b with Bu^tOK were determined and the mechanisms for carbene generation in these reactions were proposed.     

Neutrino processes in an external magnetic field in the density matrix formalism

In the matrix density formalism for a charged spinor particle located in a constant uniform magnetic field, we develop a technique for calculating the reaction rate and the four-momentum carried away from a plasma by a neutrino in one-vertex neutrino processes. Using this technique, we reproduce results for the luminosity in processes of neutrino synchrotron emission by electrons (positrons) and of electron-positron annihilation producing the neutrino pair.     

Methods for the synthesis of functionalized alkynylcyclopropanes

Data on methods for the synthesis of various classes of functionalized alkynylcyclopropanes (FACPs) reported in the last two decades are systematized. Synthetic routes to FACPs based on cyclopropanation of unsaturated compounds with various carbenes, carbenoids, and ylides are considered separately. Methods for introducing functional groups into the three-membered ring of alkynylcyclopropanes via metalation and elimination—addition processes as well as other synthetic routes to functionalized cyclopropanes are discussed.