The Cu(I)- or Ag(I)-catalyzed cycloaddition between 8-ethynyladenine or guanine nucleosides and TMSN3 gave 8-(1-H-1,2,3-triazol-4-yl) nucleosides in good yields. On the other hand, reactions of 5-ethynyluracil or cytosine nucleosides with TMSN3 led to the chemoselective formation of triazoles via Cu(I)-catalyzed cycloaddition or vinyl azides via Ag(I)-catalyzed hydroazidation. These nucleosides with a minimalistic triazolyl modification showed excellent fluorescent properties with 8-(1-H-1,2,3-triazol-4-yl)-2′-deoxyadenosine (8-TrzdA), exhibiting a quantum yield of 44%. The 8-TrzdA 5′-triphosphate was incorporated into duplex DNA containing a one-nucleotide gap by DNA polymerase β.

Abstract-A simple approach to the synthesis of 1,3-diphenylpropene isomers was developed based on Fe(acac) 3 -catalyzed cross-coupling of (E)-and (Z)-1,3-dichloropropenes with phenylmagnesium bromide.Keywords: 1,3-diphenylpropene, cross-coupling, Fe-catalyzed cross-coupling, Fe(acac) 3 ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 2, pp. 342-344. © Pleiades Publishing, Ltd., 2018. Original Russian Text © R.N. Shakhmaev, A.Sh. Sunagatullina, A.N. Vasilyeva, V.V. Zorin, 2018, published in Zhurnal Obshchei Khimii, 2018 1,3-Diphenylpropene isomers are used in organic synthesis as the starting substrates and model compounds [1][2][3][4]. The specific reactivity of 1,3-diphenylpropene is due to the presence of methylene group, being simultaneously in the allyl and benzyl positions. (E)-1,3-Diphenylpropene is usually obtained by treating a not easily accessible phenylacetaldehyde with a KOH alcohol solution [5,6], while the synthesis of less thermodynamically stable (Z)-isomer with an acceptable stereochemical purity is very problematic [7,8]. LETTERS TO THE EDITORWe investigated the possibility of obtaining 1,3-diphenylpropene 2 by Fe(acac) 3 -catalyzed crosscoupling of 1,3-dichloropropene 1 with phenylmagnesium bromide. It is known that available iron(III) salts are effective catalysts in cross-coupling reactions of Grignard reagents with vinyl [9--12] and allyl halides [13,14]. Fe(acac) 3 the most commonly used in the synthesis of natural compounds [15,16] and drugs [17][18][19][20] is advantageously characterized by low hygroscopicity, good solubility, and ease of handling [21].The reaction of (E)-1,3-dichloropropene la with 3 equiv of PhMgBr in tetrahydrofuran in the presence of 3 mol % of Fe(acac) 3 afforded a mixture of (E)-and (Z)-isomers of 1,3-diphenylpropene 2a and 2b (E : Z = 92 : 8) in a 52% yield. The introduction of the most frequently used ligands like N,N,N,N-tetramethylethylenediamine (TMEDA) [22] or N-methylpyrrolidone (NMP) [10], the replacement of THF by diethyl ether and the use of FeCl 3 as the catalyst did not substantially increase the yield of the reaction product. However, a decrease in the reaction temperature to -35°C results in an increase in the yield of 1,3-diphenylpropene to 80% with the same isomeric composition.The cross-coupling with (Z)-1,3-dichloropropene under similar conditions resulted in an isomeric mixture of 1,3-diphenylpropene (E : Z = 55 : 45) with 72% yield, while at room temperature the reaction direction shifted toward the formation of (E)-isomer (E : Z = 76 : 24). (E)-and (Z)-isomers of 1,3-diphenylpropene and diphenyl formed by homocoupling reaction were separated by column chromatography (Scheme 1).Structure and purity of the obtained compounds was confirmed by high-performance GLC analysis, NMR spectroscopy and chromato-mass spectrometry. A reliable evidence of the stereochemical configuration of isomers 2a and 2b was the values of spin-spin coupling constant of vinyl hydrogen atoms (J = 15.6 and 11.3 Hz), characteristic of the E-and Z-con...

We present the first record of Holocene fossil insect assemblages from Central Yakutia. A stratigraphic sequence in the locality within the Vilyuy River valley is a buried oxbow. The late Holocene water body inherited an impervious stratum from the late Pleistocene. The organic layer preserved rich fossil assemblages of macrofossils including insects and other invertebrates, plants, and charcoal. The ancient flora and fauna include species that are common in Yakutia as well as those that are rare and absent in the region. The most abundant finds are leech cocoons and bogbean seeds. The macrofossils of some insects were found along with remains of their host plants. Despite the absence of intensive human land use in the area, traces of fires were recorded. The oxbow represents the environment of a floodplain wetland that developed separately from the ecosystem of the adjacent sand dunes.

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