Serendipitous Formation of Various Selenium Heterocycles Hidden in the Classical Synthesis of Selenophene

Synthesis of complex di(selenophen-3-yl)diselenides and 3-methylene-3H-1,2-diselenoles directly from 1-bromobutadiynes is described. The transformation is performed under conditions used before for the synthesis of simple selenophenes from butadiynes. The reaction is operationally straightforward, and complex products were obtained in high yields. Structures of the final products were unambiguously confirmed by the means of 77Se NMR and single-crystal X-ray diffraction.

All reactions were conducted under N 2 by using standard Schlenk techniques. Glassware was pre-dried at 120 °C. Solvents were treated as follows: CH 3 CN was distilled from P 2 O 5 , Et 2 O (pure for analysis), CH 2 Cl 2 (pure for analysis), hexane (pure for analysis) were used as received. 1-Bromobutadiynes were obtained according to the known procedures. 1 Piperidine (puriss p.a.), N-methylbenzylamine (97%), 2-methylaminomethyl-1,3-dioxolane (98%), morpholine (99%), diethylamine (99%), NaBH 4 (96%), diphenyl diselenide (98%), Se (puriss p.a) and Te (99.5%) were used as received. 1 H and 13 C NMR spectra were recorded with a 500 MHz spectrometer with an inverse broadband probe. 77 Se NMR spectra were recorded with a 600 MHz spectrometer with an inverse broadband probe. A solution of diphenyl diselenide in CDCl 3 at 25 °C in a sealed capillary was used as an external standard (δ = 463 ppm). 2 For all the 1 H NMR spectra, the chemical shifts are given in ppm relative to the solvent residual peaks (CDCl 3 , 1 H: 7.26 ppm, 13 C: 77.16 ppm). Coupling constants are given in Hz. HRMS spectra were recorded using a spectrometer with an ESI ion source and TOF or ICR ion analyser. For HRMS analysis the monoisotopic m/z values and isotope patterns were calculated using enviPat 2.4. 3 80 Se was used for calculation of monoisotopic peaks.
Details of X-ray data collection and reduction X-ray diffraction data were collected with the use of ω scan technique. The space groups were determined from systematic absences and subsequent least-squares refinement. Lorentz and polarization corrections were applied. The structures were solved by direct methods and refined by full-matrix, least-squares on F 2 by use of the SHELXTL Package. 4 Non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atom positions were calculated and added to the structure factor calculations, but were not refined.
Crude ynamine was used without further purification.
Reaction with Na 2 Se. NaBH 4 (0.120 g, 3.17 mmol), selenium (0.118 g, 1.49 mmol) and water (2 mL) were placed in N 2 purged Schlenk flask. The mixture was degassed with the use of freeze-pump-thaw technique and next stirred for 30 min. at room temperature. Next ynamine was dissolved in oxygen-free MeCN (30 mL) and added to the reaction mixture. Orange solution was stirred at 60 ℃ (oil bath on magnetic stirrer with heating) for 20 h under N 2 atmosphere. After that time solvent was removed under reduced pressure and crude product was purified with the use of column chromatography (Al 2 O 3 , basic, Brockmann grade I, CH 2 Cl 2 /Et 2 O; v/v; 4/1 to pure Et 2 O). Pure 3aa was obtained as red solid (0.153 g, 0.201 mmol), yield: 67%.

X-Ray Crystallography Details
All monocrystals used for X-ray measurements were grown by slow evaporation of CH 2 Cl 2 /n-hexane solutions placed in 10 mL vials. Vials were closed using polypropylene caps with short needle pierced through the cap.