Vitus_Verdegast
Hazard to Others
Posts: 297
Registered: 5-12-2004
Location: Ottoman Empire
Member Is Offline
Mood: tea time
|
|
Sandmeyer reaction questions
Looking at :
http://www.organic-chemistry.org/namedreactions/sandmeyer-re...
They state that Sandmeyer-type reactions with thiols, water and potassium iodide don't require catalysis. Yet I was unable to find much references
describing the reaction with thiols.
I wonder if anyone has something to offer on that topic?
Also the same question goes for the reaction with formaldoxime, which gives an arylaldehyde.
I have this review, but it lacks information concerning the above:
Hodgson, H. H. Chem. Rev. (1947) 40, 251-277
It is mostly a review about different kind of catalysts used to prepare halobenzenes. They mention cyanobenzene only once.
Thanks in advance 
|
|
|
solo
International Hazard
Posts: 3967
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline
Mood: ....getting old and drowning in a sea of knowledge
|
|
I found this paper in which they use the said reactions and had some options......solo
--------------------------------------------------------------------------------------------------
2,4-Diamino-5-chloroquinazolinAe nalogues of Trimetrexate and Piritrexim:
Synthesis and Antifolate Activity
Andre Rosowsky,*?t Clara E. Mota,? Joel E. Wright,? and Sherry F. Queenerz
J. Med. Chem. 1994,37, 4522-4528
http://rapidshare.de/files/17616460/Analogues_of_Trimetrexat...
Excerp.....Sandmeyer-type reaction using KCN and CuSO4 as described in the classical paper by Davoll and Johnson(36) was found to
give erratic yields. Therefore, we developed a modified process, based on recent work in a different context by Hynes and ~o-workersI.n~ ~th is
modification, treatment of the diazotized solution of 19 with CuCVKCN instead of CuSOfiCN allowed 18 to be reliably obtained in '70% yield.
Ref: (36) Davoll, C. J.; Johnson, A. M. Quinazoline analogues of folic acid.
J. Chem. SOC1.9 70, 997-1002.
[Edited on 10-4-2006 by solo]
It's better to die on your feet, than live on your knees....Emiliano Zapata.
|
|
|
leu
Hazard to Others
Posts: 368
Registered: 13-10-2005
Member Is Offline
Mood: No Mood
|
|
The preparation of iodobenzene in Vogel's is illustrative of a reaction of a diazonium salt with potassium iodide in water Sidgewick states that cobalt or iron thiocyanate salts give better yields than the
cuprous salts in the Sandmeyer reaction when introducing the thiocyanate radical 
Chemistry is our Covalent Bond
|
|
|
caribou
Harmless
Posts: 29
Registered: 21-2-2006
Member Is Offline
Mood: No Mood
|
|
Perhaps this can be of some help:
James D. Baleja
The Facile Conversion of Aromatic Amines to Arylmethylsulfides with Methylthiocopper
Synthetic Communications, 14(3), 215-218 (1984)
https://www.synthetikal.com/hiveboard/novel/000473295.html
|
|
|
Vitus_Verdegast
Hazard to Others
Posts: 297
Registered: 5-12-2004
Location: Ottoman Empire
Member Is Offline
Mood: tea time
|
|
Thank you all very much!
I will do my own input here too but am pressed for time for the moment.
What would be most interesting is to find examples of the introduction of -SCN, -alkylthio and -CHO groups. Maybe even -OCN?
|
|
|
Sandmeyer
National Hazard
Posts: 784
Registered: 9-1-2005
Location: Internet
Member Is Offline
Mood: abbastanza bene
|
|
Formylation gives low yiled:
http://www.orgsyn.org/orgsyn/prep.asp?rxntypeid=84&prep=...
thiocyanate:
Improved Procedure to Aryl Thiocyanates: A New Synthetic Application of Dry Arenediazonium o-Benzenedisulfonimides
Margherita Barbero*, Iacopo Degani, Nicola Diulgheroff, Stefano Dughera, Rita Fochi
*Dip.to di Chimicia Generale ed Organica Applicata dell'Università, C.so M. D'Azeglio 48, 10125 Torino, Italy; E-mail: fochi@ch.unito.it
Aryl thiocyanates 3 (22 examples) were easily prepared by reaction of dry arenediazonium o-benzenedisulfonimides 1 and sodium thiocyanate (2) in
anhydrous acetonitrile at room temperature (20-25 °C) in the presence of copper powder (Procedure A) and at 50 °C or room temperature without the
metal catalyst (Procedure B). The yields were from very good to excellent in Procedure A (average yield = 83%), and from modest to excellent in
Procedure B (average yield = 63%). In comparison with the thiocyanodediazoniation carried out under traditional Sandmeyer-type conditions, the yields
of 3 were higher and the isothiocyanate isomers were formed only in traces. Moreover, the results obtained in the absence of copper confirm the role
of the anion of salts 1 as an electron transfer agent.
Barbero, Margherita; Degani, Iacopo; Diulgheroff, Nicola; Dughera, Stefano; Fochi, Rita; Synthesis; 4; 2001; 585 - 590.
Full paper: http://rapidshare.de/files/17996204/s-2001-12362.pdf.html
[...]The most traditional route for obtaining aryl thiocyanates 3 is that of diazotized primary aromatic amine reactions with metal thiocyanates
in aqueous solution, mostly under Sandmeyer-type conditions. The yields, quite often unsatisfactory, the concomitant formation of various by-products,
including the aryl isothiocyanate isomers [...]
I suppose it has interesting references on traditional Sandmeyer method. But wouldn't it be better to do Ullmann instead? Shortest still would be via
direct thiocyanation (NH4SCN/Br2), there are many refs on this reaction, see the Org. Lett paper in the post below. there is also a nice paper on this
in wanted refs thread which I requested a year ago or so. Shulgin has also done this: http://www.erowid.org/library/books_online/pihkal/pihkal155....
Using chlorine instead of bromine would give a more electrophilic species which could be used on less activated substrates in electrophilic arom.
subst.
This paper describes the traditional Sandmeyer:
Synthesis and Properties of 5-(Substituted) Mercaptotetrazoles
EUGENE LIEBER, TAKASHI ENKOJI
J. Org. Chem.; 1961; 26(11); 4472-4479.
Full paper: http://rapidshare.de/files/18022203/Synthesis_and_Properties...
I haven't seen a direct way to introduce -OCN - you'll likely need to go via diazonium -> phenol(ate) --cyanogen halide--> Ar-OCN, probably not
worth the hassle.
[Edited on 14-4-2006 by Sandmeyer]
[Edited on 14-4-2006 by Sandmeyer]
|
|
|
Sandmeyer
National Hazard
Posts: 784
Registered: 9-1-2005
Location: Internet
Member Is Offline
Mood: abbastanza bene
|
|
Ar-SCN --> Ar-SH
With dithionite:
4-iodo-phenyl thiocyanate -alcoholoc potassium hydrosulfite-> 4-iodo-thiophenol
Challenger; Collins; J. Chem. Soc.; 125; 1924; 1379.
4-chloro-2,5-dimethyl-phenyl thiocyanate --Na2S2O4--> 4-chloro-2,5-dimethyl-thiophenol
Patent; I. G. Farbenind.; DE495879.
1-(4-Thiocyanophenyl)pyrrolidine --Na2S*9H2O,NaOH/EtOH/4h--> 4-pyrrolidin-1-yl-benzenethiol
Yield 89%
Kmonicek, Vojtech; Svatek, Emil; Holubek, Jiri; Protiva, Miroslav; Collect. Czech. Chem. Commun.; 51; 4; 1986; 937-947.
With NaBH4:
2-methyl-4-octyloxy-1-thiocyanato-benzene -NaBH4/EtOH-> 2-methyl-4-octyloxy-benzenethiol
Okamoto, Hiroaki; Wu, Jianwei; Morita, Yuki; Takenaka, Shunsuke; BCSJA8; Bull. Chem. Soc. Jpn.; 75; 1; 2002; 175 - 180.
(2-tert-butoxycarbonylamino-5-tert-butyl-4-thiocyanato-phenyl)-carbamic acid tert-butyl ester -NaSH/NaBH4/MeOH->
(2-tert-butoxycarbonylamino-5-tert-butyl-4-mercapto-phenyl)-carbamic acid tert-butyl ester
Prasad, J. V. N. Vara; Org. Lett.; 2; 8; 2000; 1069 - 1072.
Fullpaper: http://rapidshare.de/files/18023556/Synthesis_of_Heterocycli...
With NaOH:
2-thiocyanato-benzaldehyde -NaOH-> 2-mercapto-benzaldehyde
Yield 70 %
Marini, Peter J.; Murray, Keith S.; West, Bruce O.; J. Chem. Soc. Dalton Trans.; 1983; 143-152.
[Edited on 14-4-2006 by Sandmeyer]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
