Re: ORGLIST: Isocyanates....

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From: Sachin Chaphekar (purvi_chaphekar$##$yahoo.com)
Date: Thu Jul 26 2007 - 00:45:39 EDT

Hi! Normally if you prepare a amine.HCl salt and then do the phosgenation you end up with higher yield. If you use free base the fate of reaction will depend on how you mix amine and triphosgene and temp. of mixing. HCl salt also allows you to work directly at higher temperatures. Please check general literature like in Ullmann's encyclopaedia reagrding isocyanate you will get some clues. The reaction your are doing is very fast and depends only on purity of isocyanate obtd. Good luck, Sachin ----- Original Message ---- From: Ohad Ilovich <ilovich$##$pob.huji.ac.il> To: everybody$##$orglist.net Sent: Tuesday, July 3, 2007 9:03:32 PM Subject: ORGLIST: Isocyanates.... Dear all, I have asked about creating an urea here before and recieved some help in the matter and decided to try my luck once again. I have two questions: 1) I have an aniline which i react with triphosgene to form an isocyanate. this isocyanate is then reacted with another aniline (picomolar amounts of a radioactive aniline) to form an urea bond. I cannot seem to get a good isocyanate. sometimes when i add the second aniline i get a complete reaction in 30 mins at room temp. and sometimes no reaction at all. Is there a way to isolate the isocyanate? Is there a way such as IR to make sure it is pure isocyanate? Can i do column chromatography in a glove box? we can buy high-purity isocyanates so there must be a way to do this.... 2) can anyone give me any further ideas about precursors for urea bond formation? I have tried isopropenyl as a leaving group without much success and I know CDI is used (but mostly aliphatic amines) any ideas and referance aritcles will be most welcome Ohad Ilovich ************************************************************************************ This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses. ************************************************************************************ ____________________________________________________________________________________ Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos & more. http://mobile.yahoo.com/go?refer=1GNXIC


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