By the way, is there a way in which I can import a structure, say from Chemdraw?
I have a C-8 chain with a secondary alcohol, a terminal alkyne and a double bond somewhere in the middle as well. I want to add a single carbon and another alcohol group to the terminal end of the alkyne. In pursuit of this purpose I use two equivalents of Butyl Lithium (first eq for the secondary alcohol), and paraformaldehyde, but I get very poor yield. I leave the reaction overnight at 30-35 degrees, and it is under Ar from the start of course. My supervisor doesn't think that leaving it any longer will improve the yield. I have tried with adding even up to 1.7 eq of paraformaldehyde (which I have ground and put on a vacuum pump to dry)
as well as slightly more than 2 eq BuLi, but if at all the extra BuLi only worsened it.
The dryness of the paraformaldehyde does have an influence, but it still gives a low yield even if I grind it very hard and leave it on the pump for at least a day. My supervisor has done a similar reaction, but in her case the secondary alcohol is protected by TBS, and this gives a respectable yield. Someone also suggested that the H on the terminal alkyne forms a bridge with the deprotonated secondary alcohol after the first equivalent of BuLi is added, and so it is not properly deprotonated by the second eq of BuLi. However, the mixture supposedly becomes a darker shade of yellow when the dianion is formed and this I have seen-it's not my imagination or over-eagerness.
This is the formula of the reagent:
This is the formula of the proposed product:
Any suggestions as to why I may be getting such a low yield? Also, what would be your gutt feeling, should I leave the reaction a bit longer or what? Do you agree with the theory of the bridged H?