tag:blogger.com,1999:blog-51846086760422068.post3349206540061142300..comments2024-03-28T08:37:08.964-07:00Comments on Open Flask: Maoecrystal V, or I how I learned to cope with my mediocrityBaranLabhttp://www.blogger.com/profile/01806245988209508968noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-51846086760422068.post-22143678686285731792017-12-05T12:41:06.251-08:002017-12-05T12:41:06.251-08:00This comment has been removed by the author.Anonymoushttps://www.blogger.com/profile/17810258094400415858noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-33409294539184423372017-12-05T12:41:04.412-08:002017-12-05T12:41:04.412-08:00Were you able to get to a chiral beta keto trifluo...Were you able to get to a chiral beta keto trifluoromethyl ketone bearing an alkyne (line 2, scheme 1), or were the conia-ene investigations with racemic material?<br /><br />Anonymoushttps://www.blogger.com/profile/17810258094400415858noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-11023030484810349232017-06-20T23:01:41.088-07:002017-06-20T23:01:41.088-07:00Very helpful suggestions that help in the optimizi... Very helpful suggestions that help in the optimizing website.<br /> thank for sharing the link<br /> <a href="http://www.tshyshz.com" rel="nofollow">gclub online</a><br /> <a href="https://goldenslot.gclub-casino.com//" rel="nofollow">goldenslot</a> Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-51388531189332069422016-08-06T07:16:53.637-07:002016-08-06T07:16:53.637-07:00Dear Artiom,
In how many years did you complete t...Dear Artiom,<br /><br />In how many years did you complete this project? Anonymoushttps://www.blogger.com/profile/18439365537300853862noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-61446918543224977832016-08-03T21:14:38.148-07:002016-08-03T21:14:38.148-07:00Thanks for your answers and your comments about di...Thanks for your answers and your comments about discodermolide, more hair falls out when I even think of that one. <br />So the preparation of compound 7 does not seem that problematic or at least nothing that could not be optimised.<br />The yield of the pinacol, 45% and the side product 22% still leaves missing mass. Was this isolated or was it just "polymer"?<br />Now I realise that you needed material for the various reaction screening and so on, but with surely enough on hand why only make 54mg of 1? Surely a couple of grams would have been possible? A 75% yield is not bad at all for such a complex sequence.<br />You got an x-ray, which solvent did you use to obtain the single crystal, or did you use Fujita's methodology?Anonymoushttps://www.blogger.com/profile/15287977920784124907noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-6664742861349160602016-08-03T06:36:05.478-07:002016-08-03T06:36:05.478-07:00I was looking at the very first step (prep of 7). ...I was looking at the very first step (prep of 7). It seems like everything is crucial here! Questions: Just how profound is the solvent system, in the experimental you used a 1:1 mixture of toluene and MeTHF. What happens if it is 1:2 or 2:1, etc?<br />Also you add the Grignard over 4 hours, what happens to the quality and yield of 7 if you do it faster or slower? Also just how critical is the temperature here, adding such a large volume over 4 hours did you not observe deviation from -78°C? I also noted that this reaction seems to be very dilute, any idea if it works just as well much more concentrated?<br />Thanks, congrats of a great piece of work.<br />QuintusAnonymoushttps://www.blogger.com/profile/15287977920784124907noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-29872520936543325302016-07-28T13:59:56.486-07:002016-07-28T13:59:56.486-07:00it could be I am wrong, but I think it would be a ...it could be I am wrong, but I think it would be a combined effect of removing free cyanide and generating TMS-iodide. For this mechanism to be operational, you also need to inhibit initial cyanohydrine formation by scavenging free cyanide. Since TMSCN is a decent silylating agent on its own right and undergoes alcoholysis with a primary alcohol almost instantly, and since you do have one unprotected hydroxymethyl group in the substrate that gets silylated, you generate one extra equivalent of HCN in the reaction mix right at the beginning - an equvalent that needs to be mopped up or evaporated before this alternative cyclization can take place.<br /><br />I guess the easy way to test it would be to expose the material to excess of TMSCN without any catalyst, evaporated the O-silylated product to remove HCN and then add fresh TMSCN and TMSI. Or treat it with TMSI alone, to see if you can isolated any cyclized product with a skeleton that is the same as 28 but without the cyano groupmilkshakehttps://www.blogger.com/profile/08188961610554710616noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-5972703918912410732016-07-27T23:54:08.606-07:002016-07-27T23:54:08.606-07:00I think there is an alternative explanation for th...I think there is an alternative explanation for the formation of product 28 with TMSCN + I2: It is not that CN suddenly attacks the more hindered carbonyl, but rather that initial cyanohydrine formation is inhibited in the presence of iodine (scavenging free CN- as cyanogen iodide). I also think in situ formed TMS-iodide as a powerful silylating agent activates the less hindered carbonyl by carbonyl silylation, which then (in the absence of free CN-) accepts the more hindered ketone carbonyl as a nucleophile. The resulting cyclized oxo carbenium cation should be fairly stable but eventually ends up abstracting CN from TMSCN. The facial selectvity in this case is probably due to thermodynamic control and the strain of the cyclic system (the other two conceivable stereoisomers of 28 would be more strained). <br /><br />Also, a very impressive problem-solving and optimization work, and with just two chemists. milkshakehttps://www.blogger.com/profile/08188961610554710616noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-57439375283390952582016-07-27T13:34:35.074-07:002016-07-27T13:34:35.074-07:00congrats ! awesome work. congrats ! awesome work. Anonymoushttps://www.blogger.com/profile/02382039503258350189noreply@blogger.comtag:blogger.com,1999:blog-51846086760422068.post-34938453602350541452016-07-27T08:37:06.609-07:002016-07-27T08:37:06.609-07:00Seems like whenever you weren't telescoping, y...Seems like whenever you weren't telescoping, you got x-rays! Fantastic work.Anonymoushttps://www.blogger.com/profile/11392348927411012865noreply@blogger.com