Uh, yeah but --- are there any substitutes for sodium cyanoborohydride in the reductive formylation of tryptamine? Very seldom can a reduction be limited to only one possible reagent. I recall someone asking about, or rather mentioning, catalytic hydrogenation in this context, but not answered. The problem is cyclization, I believe, happening with overly vigorous reduction.
Lilienthal, your answers are always so authoritative they seem to still further discussion. Yet they are so terse, they leave me hungering for further details. Quite similar to your website! (particularly for someone without chem library access.) I would love to see you post some general overviews on tryptamine chemistry. These compounds are sly and tricky to an extraordinary degree, for they are exceptions to so many general principles of chemistry that they must bee ensorcerelled!
Reduction is the keystone. I am tired of hearing about lithium aluminum hydride, when you know we can't get any. I know there must be two-step reductions of an indole glyoxylamide to the amine, without LAH; what are they? Would lithium borohydride work for the one-step reduction as well as LiAlH4, as in smiley_boy's
Post 196781
(smiley_boy: "Re: One more idea for LAHless nitrostyrene reductions", Novel Discourse)
Re: One more idea for LAHless nitrostyrene reductions
...under aprotic conditions you can combine NaBH4 and add a little LiCl (or better yet LiBr) to obtain LiBH4 in situ - a much, much more powerful reducing agent.
Here's a quick, overly-simplified lesson on the chemistry of borohydrides and aluminum hydrides and their activity. When the metals complex with BH4- or AlH4-, the relative size of the metal atoms has a huge effect. For example, with Li+, the overlap of electron orbitals around the Li is much too small to really overlap much with BH4-, plus lithium is not so free-and-easy with giving up its elecxtrons like a cation is supposed to (at least compared to other metals.) The result: the borohydride is very reactive. LiBH4- readily reacts with water or simple alcohols, just like LiAlH4. LiBH4 can reduce nitro groups to amino groups.
or his mention of borane-THF Post 196785
(smiley_boy: "Re: One more idea for LAHless nitrostyrene reductions", Novel Discourse)
Actually, speaking of borane, that seems like a topic that hasn't been as well addressed as I feel it should. Now, correct me if I'm wrong, but borane*THF can be produced from sodium borohydride by partial decomposition with sufuric acid in THF:
2 NaBH4 + H2SO4 + 2 THF -> 2 BH3*THF + Na2SO4 + 2 H2
So why isn't this taken advantage of? The reduction of nitrostyrenes using borane-ether complexes is a well-established procedure in the literature, providing good yields and remarkable chemoselectivity; for some arylethylamines, its the only practical route. So why aren't people experimenting with this around here? Am I forgetting something?
To make myself more clear, this is what I'm proposing: you can replace the LiAlH4 in your average nitrostyrene reduction procedure with NaBH4 and H2SO4! Safe, cheap, available. How's that for practical? Hopefully this generates some interest...
Likewise, in this reductive formylation of tryptamine, what is the key to making this feasible for more beez? Converting sodium borohydride to cyanoborohydride is not totally beyond reach, but no one likes working with cyanide at all, at all. I hate having this feeling that you know these secrets, but are just too haughty to tell us. If you were just more verbose in your posts, filling us in with greater detail, your work could serve more as a catalyst for cooperative discoveries rather than so many discouragements.
Excuse the critical tone. I know you like to maintain only the highest caliber of technical excellence in every statement you make. But I wish you could unbend a little, and try to help us out here. What about an informal review of reducing agents used in making tryptamines? We want to find a way through this maze: a way we can make tryptamines, without owning stock in a chemical distributor.
turning
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