ne, nebude. Proto se to bude muset izolovat, okyselit a pak zahřát. Proto to zůstane ve formě alkoholu. Kdyby to dekarboxylovalo už v jednom kotli, tak se to pravděpodobně bude dál oxidovat na keton přímo. Příště to budu muset víc rozepisovat.

BORAG: bude dekarboxylovat aj deprotonizovana (ako benzilat)?

ech, moment. Ještě k té kontrakci. V prvním kroce se to oxiduje na benzil, pak dochází k přesmuku na alfa-hydroxy-karboxylovou kyselinu, která následně dekarboxyluje (bude to potřeba zahřát).

jj. Mám takový pocit, že právě keton podléhá postupné redukci lépe než alkohol. Ale muselo by se to zkusit. Možná to nebude ani potřeba.

BORAG: hui :) zaujimava je ta kontrakcia benzoinu alkalickou oxidaciou. tam dojde k oxidaciu na benzil, presmyku na benzilat a jeho oxidativnemu odburaniu?
a naco oxidujes (? -- PCC) ten difenylmetanol pred komplet redukciou jodovodikom?

Dělal bych to nějak takhle. To že se v předposledním kroce používá cín si pamatuju z nějaké toxikologie. Jinak bych to vážně nedal :-) Příprava toho dibromderivátu je taky taková, hmm, divná. Nic lepšího mě nenapadlo..

a ked sme uz zasli do tych iritantov, skuste vymysliet (len na prvy pohlad trivialnu) metodu pripravy latky Excalibur (dihydrochlorakridarzinu):

jo, to je fakt. Já si pořád nějak neuvědomuju, že v tomhle případě se bavíme o průmyslové výrobě :-)

BORAG: ja by som povedal, ze technicky salicylaldehyd pri odbere niekolkych ton bude celkom lacny. :)

http://www.acros.com/DesktopModules/Acros_Search_Results/Acros_Search_Results.aspx?search_type=CatalogSearch&SearchString=salicylaldehyde

1kg za 60 Eur, to jeste jde, ne..

LIBRIUM: teda to mě docela překvapuje. Spíš co se ceny látek týče. Používáš chlornitrobenzen, ten je tedy asi o stovku levnější než mnou použitý nitrofenol (resp. jeho redukovaná forma). Druhým reagentem je v tvém případě salicylaldehyd a ten jsem před nějakou dobou potřeboval a byl docela nepříjemně drahý. Já volil chlorbenzaldehyd, tam bych tak kilo tipoval na 1500.

nie som si uplne isty, ale myslim, ze takto nejak ho vyrabali Briti pre potreby armady a policajnych zloziek.

Mel bych novy navrh pro chemiky. Obrazky stale neumim, takze snad to pujde takto. Je to lakrimator - latka CR. (dibenzo-1,4-oxazepin)

jaj, no...dost casto plati pravidlo, ze ked nieco mozes urobit v jednom kroku s +- podobnym vytazkom a cistotou, tak "rozporcovanie" do viacerych krokov, pokial nedocieli vyrazne vyssiu ucinnost, selektivitu atd je to be omitted.

LIBRIUM: No, uz jsem nenasel vytezek te "druhe" redukce, ale mozna mas pravdu.. 2 stepy i ve vysokem vytezku dost srazi overall vytezek.. a navic proc delat 2 stepy, kdyz to jednim jde jednodusse a ve slusnem vytezku.

zatimco LAH si tak dobre nevede..

20 grams of LAH was added to 200ml THF in a 1000ml two-necked RB flask, equipped with a magnetic stirrer, and it fizzed some, but not much. Now 20 grams of the above nitrostyrene was added dropwise as a solution in 200ml THF through a dropping funnel, which caused the solution to boil, and when all had been added, the solution was allowed to reflux for 24 hours. The reaction mixture was allowed to cool, and 15ml IPA, followed by 15ml 15% NaOH solution, 30 ml THF, and finally 50ml of cold water, as fast as the exothermic reaction allowed. The solution now became a white sludge, which was filtered through a pad of celite, and the filter cake washed with some additional THF. The solvent was removed under vacuum, and the residue dissolved in dilute H2SO4, and washed with 3x25ml CH2Cl2, made basic with 25% NaOH solution, and extracted with 3x30 ml CH2Cl2. The extracts was dried over MgSO4, filtered, and the solvent removed under vacuum. The residue was distilled at 3 mmHg to give 10 grams (57%) of a slightly yellow oil, 2,4-dimethoxy-3-methylphenetylamine.

WILDENBURY_SQ: no a prave, ked si tie dva kroky spocitas, vyjde ti max. 78.7% vytazok, ak su ti bohovia nakloneni a s predpokladom, ze tu zadany substrat pobezi rovnako dobre alkebo lepsie...proste si stale myslim, ze one-pot redukcia rovno na amin by bola lepsia...

LIBRIUM: citacia jen pochybne reference narkomanu z volne pristupnych "chemickych" webu :) Solidni reference ve skole, kde ted nejsem..

1-(2-fluorophenyl)-2-nitropropane

4,15g NaBH4 stirred happily in 50ml EtOAc and 10ml EtOH at 15°C. 5g 1-(2-fluorophenyl)-2-nitropropene was added in small portions. Be careful here! The first 250mg or so caused a violent bubbling, much more than the earlier ones. The temp rose 8°C from that small portion. Wierd! When 1/3 had been added the suspension turned to a thick white paste which had to be diluted with more EtOH. So another 10ml EtOH was added. Kept on adding happily, but kept a close eye on the temp. When 2/3 was added, another 10ml EtOH had to be added. Paste again! The total amount of EtOH added was 30ml. This will cause a problem in the workup since it will carry the ester and some product over to the water phase. This time I destroyed the borohydride with dropwise addition of diluted acetic acid to the rxn vessel. When this was done, 100ml toluene was added together with 50ml brine. The solvent layer washed two times with water, once again with brine, dried and stripped of solvents in a rotovap.

Yield; 4,3g (84,9%) 1-(2-fluorphenyl)-2-nitropropane as a clear yellow oil. Purity; 97% (HPLC)



1-(2,4,5-trimethoxyphenyl)-2-nitropropane

25,3g (100mmol) 1-(2,4,5-trimethoxyphenyl)-2-nitropropene was added portionwise to a suspension of 11,4g (300mmol) NaBH4 in 150ml AcOEt and 43,2ml (1,2mol) EtOH @ 20-25 deg C. An ice-water bath needed to cool the reaction mixture. The addition took 25 minutes. It was the allowed to stir at room temp for an additional 20min. Excess borohydride was destroyed with diluted acetic acid. When gas evolution ceased 100ml toluene and 150ml brine was added. The organic phase was washed twice with water (2x100ml) and once again with 100ml brine. The solvent was dried with MgSO4 and stripped off in a rotovap. The residue solidified to a clear yellow cake. This cake was dissolved in 150ml MeOH which gave a bright yellow solution. To this solution 500ml ice-cold water was added. This gave in 5min a thick slurry of colorless fluffy crystals which were filtered off and dried.

Yield 23,7g (92,9%) 1-(2,4,5-trimethoxyphenyl)-2-nitropropane