Trimethyloxonium salts (When it absolutely, positively, must be methylated)

When you take organic chemistry, you learn about methyl iodide for putting on a methyl group. Eventually, though, if you stick with chemistry, you need an alkylating agent for grown-ups.

There's a lot of good ones, including dimethyl sulfate, methyl triflate (PDF), and the ever-so-toxic "magic methyl," methyl fluorosulfonate.

Part of being a grown-up, though, is settling down with an alkylating agent, and aside from the odd dirty weekend with some of the more exotic compounds, it's trialkyloxonium salts for me:


We used to have coffee together in the morning, but the methanol got to me...


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You know, given the hazards inherent in methylating agents, I do believe you missed a chance at a primo Tarantino reference -- "when you absolutely, positively have to methylate every mofo in the room."

there is a lovely method for making triethyloxonium tetrafluoroborate in Org Syn. You just mix together BF3 etherate, dry ether and epichlorohydrin. The stuff crashes out. I did it on a 50g scale.

You get trimethyl oxonium from triethyloxhonium just by blowing dimethylether gas stream over it. The alkyls exchange, bitches...

What? No methyl lithium?