Synthesis of photochromic 1,2-dihetarylethene using regioselective acylation of thienopyrroles

[formula: see text] The influence of catalysts, acid chlorides, and solvents in the acylation of methyl 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied. Conditions for the regioselective acylation processes were found. Thienopyrrole-based photochrome was synthesized for the first time.     

Supersonic turbulence and structure of interstellar molecular clouds

The interstellar medium provides a unique laboratory for highly supersonic, driven hydrodynamic turbulence. We propose a theory of such turbulence, test it by numerical simulations, and use the results to explain observational scaling properties of interstellar molecular clouds, the regions where stars are born.     

Continuous time vertex-reinforced jump processes

 We study the continuous time integer valued process , which jumps to each of its two nearest neighbors at the rate of one plus the total time the process has previously spent at that neighbor. We show that the proportion of the time before t which this process spends at integers j converges to positive random variables V _j , which sum to one, and whose joint distribution is explicitly described. We also show Received: 19 December 2000 / Revised version: 1 November 2001 / Published online: 17 May 2002     

Subgraphs with Restricted Degrees of Their Vertices in Planar 3-Connected Graphs

We have proved that every 3-connected planar graph G either contains a path on k vertices each of which has degree at most 5k or does not contain any path on k vertices; the bound 5k is the best possible. Moreover, for every connected planar graph H other than a path and for every integer m ≥ 3 there is a 3-connected planar graph G such that each copy of H in G contains a vertex of degree at least m.     

Nuclear magnetic resonance spectra of mixtures of 2-monohydroperfluoroisobutane and triethylamine

Conclusions The presence of a strong hydrogen bond between 2-monohydroperfluoroisobutane and triethylamine has been established by the NMR method. Thehydrogen bond shift in this system is not less than 2 p.p.m.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1342–1343, June, 1967.     

Improved synthesis of arachno-6,9-C2B8H14 and its halogenation under electrophilic conditions

A convenient synthesis of arachno-6,9-C₂B₈H₁₄, based on the reduction of nido-5,6-C₂B₈H₁₂ with sodium tetrahydroborate, is reported. Electrophilic halogenation of the former carborane produced a series of 1-X-6,9-C₂B₈H₁₃ (X = Cl, Br and I) derivatives whose constitution was established on the basis of their ¹H and ¹¹B NMR spectra.