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Cycloselenation of sodium acetylide; 2-Methylene-1,3-diselenole

SyntheticPage 416
DOI: 10.1039/SP416
Submitted May 28, 2010, published May 28, 2010
Nikola Paul Chmel (n.chmel@warwick.ac.uk)
A contribution from Scott group, Warwick University


			Reaction Scheme: Cycloselenation of <SPAN class=csm-chemical-name id=csm1288649638974 title="sodium acetylide">sodium acetylide</SPAN>

Chemicals Used

Sodium acetylide (washed with diethyl ether and pentane, dried)
Selenium powder
THF (distilled over potassium, degassed)
MeOH (distilled over magnesium methoxide, degassed

Procedure

Sodium acetylide (2.4 g, 0.05 mol) was suspended in dry THF (50 ml) under argon and cooled to -78°C. Selenium powder (3.8 g, 0.048 mol) was added and the mixture was allowed to warm to 0°C and was stirred for 1 h. The mixture was cooled to -78°C and MeOH was added dropwise (30 ml). The mixture was stirred for 15 min and was allowed to warm to 0°C and was stirred for another 2.5 h. From this point on all of the operations were performed in the dark. All of the solutions used were kept at 0°C at all times. The mixture was quenched with water (60 ml) and extracted with pentane (5 ×30 ml). The combined organic extracts were washed with water (2 × 30 ml) and dried over Na2SO4. The solvents were removed in vacuo without heating. Obtained red solid was immediately used in the following reaction or stored overnight under nitrogen, in the dark at -30°C. Yield 2.4 g (24%).

Author's Comments

Reaction performed several times with various yields - the extraction part needs to be executed as fast as possible - it's crucial to keep the temperature down and protect from light. This is an intermediate in synthesis of tetraselenafulvalene here

Data

1H NMR (400 MHz, 298 K, CD2Cl2) δH 6.97 (dd, JHH = 1.1 Hz, CH=CH), 5.65 (dd, 2H, JHH = 1.1 Hz, C=CH2).

13C NMR (100 MHz, 298 K, CD2Cl2) δC 120.5 (CH=CH), 108.2 (C=CH2), (C=CH2 peak missing)


Lead Reference

K. Takimiya, H. J. Jeon and T. Otsubo, Synthesis, 2005, 2005, 2810-2813

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Get structure file (.cdx, .sk2, .mol)

Keywords: addition, alkynes, heterocyclic compounds, tetraselenafulvalene

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