Author Topic: Synthetic challenge -Rhodium  (Read 1493 times)

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dormouse

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Synthetic challenge -Rhodium
« on: April 19, 2000, 05:47:00 PM »

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Author  Topic:   Synthetic challenge 
Rhodium
Administrator   posted 11-07-1999 11:58 AM          
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Suggest a synthesis of one or more of the following molecules, preferably without using alkyl-lithium reagents:
 


Gaston
Member   posted 11-08-1999 10:06 AM          
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5-Brominate o-cresol and go on as with safrole synth.
 
Rhodium
Administrator   posted 11-08-1999 11:37 AM          
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Won't work. Methoxy is a stronger o,p-directing group than Methyl. The bromine will place itself in the 4-position instead.
 
K.C. Nicolaou
Member   posted 11-08-1999 11:51 AM          
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How about a short list of acceptable precursers?
 
Osmium
Member   posted 11-08-1999 11:55 AM          
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There is only one synth I found for the allylbenzene:
Helv. Chim. Acta 56, 1973, 75-105
via Grignard from 5-chloro-2-methyl-anisole and allyl bromide

For the benzaldehyde, check the following:
J. Prakt. Chem./chem. Ztg. 336, 3, 1994, 255-59
Liebigs Ann. Chem. 7, 1985, 1413-21
J. Chem. Soc Perkin Trans 1, 1980, 1607-13
Chem. Pharm. Bull 38, 7, 1990, 1852-56
J. Med. Chem. 13, 1970, 26-30
Chem. Pharm. Bull. 10, 1962, 856-65
J. Het. Chem. 12, 1975, 889-92
Chem. Pharm. Bull. 26, 1978, 2175-80

Don't know which methods are used in these refs, some of them invariably will use R-Li reagents.
What's wrong with BuLi et. al.? Afraid?


 
Gaston
Member   posted 11-08-1999 01:15 PM          
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JFI: Are there methods changing o,p-directivity, analog to protecting groups?
 
Acme
Member   posted 11-12-1999 02:18 PM          
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From 3-Methoxybenzaldehyde, which is commercially available, use iodomethane.
Commins, Brown JOC 49,6 1984 p1078-1083


Acme
Member   posted 11-12-1999 05:01 PM          
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Sorry, they get the pdt 66%, but with sec-BuLi, & TMEDA.
 
Rhodium
Administrator   posted 11-12-1999 05:27 PM          
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I got a better synth in E-mail:
Brominate 4-methylbenzaldehyde with one equivalent of bromine in the presence of FeBr3. The 3-position is favored by both substituents, so that would go just fine.

Then react the aryl bromide with NaOMe in the presence of a Cu(I) halide, and the desired benzaldehyde will be produced in good yield.

It was as simple as that, apparently.


Osmium
Member   posted 11-15-1999 11:49 AM          
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Those compounds surely sound interesting, same effect as MDMA without the toxic component. Do you know somebody who will try them out? If so, tell him to use Mg dissolved in dry MeOH instead of NaOMe, to make it more OTC for the other bees.
Thinking about it, I think I saw some 4-alkyl-BA's last week. There definitely was a bottle of 4-Et-BA, I think I'll rescue it from an uncertain fate in legitimate science!
 
Gaston
Member   posted 11-21-1999 10:01 PM          
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Is it the propenyl/aldehyde or the amine that´s like MDMA? Latter i guess, huh?
 
Rhodium
Administrator   posted 11-22-1999 08:38 AM          
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Yup, the amine.