[kanonsviel]

Hi, all,

Is there anybody who has done a typical Brown crotylation with a reaction rate higher than 60% or so?
If so would you please give me some tips as to how to dissolve the 2-butene into the THF solution?

I actually did this several times but the reaction rate are very crappy, I believe I followed the original procedure very strictly except that I don't know how they dissolve the 2-butene and I'm suspecting this may the reason why I'm getting a low reaction rate.

Here is how I do it:
Cool the THF down to -78 °C, insert a N2 balloon, insert a needle close to the solvent surface, flash 2-butene from that needle.

Other tips to enhance the reaction rate are also welcome.

Thanks.

[TheUnassuming]

When you say rate, do you mean yield? What are the stated yields from the paper you are following?  How different is your substrate from the papers? 
If you mean rate then increase the temperature to increase the rate of the reaction, or increase concentration of the reactants. 
I've never done that specific reaction before, but I've done reactions with various gas's before.  I've always "bubbled" my gas into the reaction as opposed to just blowing it onto the surface.  Not sure how much of a difference that will make for you but its worth a try on small scale to see. 

[kanonsviel]

I believe the yield in the original paper was something higher than 70%.
Thanks for the tip, I will try and see how it works

[TheUnassuming]

If the paper you are following only reports 70% yield than I wouldn't expect much better with your substrate.  I've had it happen before but its more the exception than the rule.
Good luck!