solubility is low even in these solvents. The main part of bromide 1 stays as a solid during the reaction and
remains unconverted. The use of methanol as solvent increased the solubility of bromide 1;, however, when we
carried out the reaction of bromide 1 with divinyl selenide in methanol, the formation of heterocycle 2 was not
observed. Raising the temperature of the reaction increased the solubility of bromide 1 but caused formation of
by-products. When the reaction was carried out at room temperature for 40 h (instead of 20 h), the obtained
product 2 was contaminated with some impurities.
Thus, the annelation of the dihydro-1,3-selenazole ring to pyridine, which is based on the reaction of
2-pyridylselenenyl bromide with divinyl selenide, was accomplished for the first time. The use of divinyl
selenide permitted us to obtain the annelated product containing the reactive vinylselanyl group.
1H, 13C, and 77Se NMR spectra were recorded on a Bruker DPX-400 spectrometer (400, 100 and
1
76 MHz, respectively) in D2O; external standards were HMDS (for H and 13C NMR spectra) and Me2Se
(0.0 ppm, for 77Se NMR pectrum). Divinyl selenide is ready accessible from elemental selenium and acetylene
[10, 11]. Elemental analysis was performed on a Thermo Finnigan ЕА 1112 Elemental Analyzer. Melting point
was determined on a Boetius hot stage apparatus (PHMK 05 VEB Wägetechnik Rapido). Bis(2-pyridyl)
diselenide was obtained from 2-bromopyridine and selenium [12].
3-(Vinylselanyl)-2,3-dihydro[1,3]selenazolo[3,2-a]pyridin-4-ium Bromide (2). A solution of bromine
(80 mg, 0.5 mmol) in acetonitrile (2 ml) was added dropwise to a cooled (an ice bath) solution of bis(2-pyridyl)
diselenide (157 mg, 0.5 mmol) in MeCN (4 ml). The mixture was stirred for 1 h on the ice bath and for1 h at
room temperature. A solution of divinyl selenide (133 mg, 1.0 mmol) in MeCN (2 ml) was added to the obtained
suspension of bromide 1, and the mixture was stirred for 20 h at room temperature. The precipitate was filtered
off to give unconsumed bromide 1 (190 mg, 20% conversion). The solvent and divinyl selenide were distilled
off from the filtrate. The residue was washed with hexane and dried in vacuum. Yield 73 mg (19.7%, 98% based
1
on consumed bromide 1). Yellowish powder, mp 166-169 ºC (decomp.). H NMR spectrum, , ppm (J, Hz):
3.87 (1Н, dd, 2J = 11.7, 3J = 5.6) and 4.27 (1Н, dd, 2J = 11.7, 3J = 7.0, SeCH2); 5.67 (1Н, d, 3J = 16.7) and 5.88
(1Н, d, 3J = 9.1, =CH2); 6.64 (1Н, dd, 3J = 7.0, 3J = 5.6, N+CHSe); 6.82 (1Н, dd, 3J = 9.1, 3J = 16.7, SeCH=);
7.57-7.62 (1Н, m, H Ar); 7.96-7.99 (1Н, m, H Ar); 8.02-8.08 (1Н, m, H Ar); 8.80-8.84 (1Н, m, H Ar). 13С NMR
spectrum, , ppm: 31.5 (SeCH2); 71.2 (SeCH); 120.9 (=CH2); 123.8 (C Ar); 127.6 (SeCH=); 128.8 (C Ar); 142.6
2
(C Ar); 144.0 (C Ar); 157.9 (C Ar). 77Se NMR spectrum, , ppm (J, Hz): 407 (2JSe–H = 9.5, JSe–H = 15.9,
SeCH2); 474 (2JSe–H = 13.5, 2JSe–H = 16.7, CHSeCH=). Found, %: С 29.56; Н 2.91; N 3.58; Br 21.32; Se 43.02.
C9H10NBrSe2. Calculated, %: С 29.22; Н 2.72; N 3.79; Br 21.60; Se 42.68.
Financial support of the Russian Foundation for Basic Research (grants Nos. 10-03-00543 and 10-03-
92666) is gratefully acknowledged.
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