My colleagues dissolved Selenophene in anhydrous ether and cooled to -78 oC. n-BuLi was then added dropwise while the mixture was being stirred continuously for 1.5 h at –78 oC. One portion of sulphur powder was added and then the mixture was stirred continuously for 2 h at –78oC. 1-BromoR (R= C6H14, C10H22 and C12H26) was added dropwise while stirring and then left to stir overnight at room temperature. The desired product was the R group attached to the S which is attached to the alpha position on the ring. This was obtained for 2 of the reactions however, we obtained an open chain with no sp2 hybridised carbons.
Furthermore, we carried on with the expected products and added n-BuLi in anhydrous THF at –78 oC under nitrogen and stirred for 1.5 h. Tributylstannyl chloride was added and left to stirred for 6 h at room temperature. The reaction was terminated by adding water. The desired product would be the organotin attached to the alpha position on the opposite side of the ring but we obtained an open chain with no sp2 hybridised C.
This reaction was taken from the literature and carried out with thiophene which has very similar reactivity to selenophene.
Can anyone explain this? why does the ring open? could it be due to the T not being maintained at -78 oC?
Yes, Temperature has a role in getting the other product. The next thing would be to check that the reactants and medium (solvent and atmosphere both) are moisture free, and the phases are inert with no trace of water.
Nice to hear the explanation, question and answer. I think so. Thank you very much.
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