Chiral thiourea and bis ( thiourea ) catalysts can be effective in DABCO-catalyzed MBH and aza-MBH reactions.
22.
A more convenient route to 2-mercaptopyridine is the reaction of 2-chloropyridine and thiourea in ethanol and aqueous ammonia.
23.
The toxicity was proposed to arise from the thiourea group, and similar guanidine analogues were investigated until the ultimate discovery of cimetidine.
24.
Unlike urea and thiourea, which have both been researched extensively, mainly qualitative and comparative information on selenourea s tautomerization is available.
25.
While simple thiourea requires a nucleophilic catalyst in conjunction, bifunctional catalysts such as phosphine-thioureas can be used alone for asymmetric MBH reactions.
26.
The equilibrium mixtures at 150 �C and 180 �C contain 30.3 % and 25.3 % ( by weight ) thiourea, respectively.
27.
A goitrogenic effect ( enlargement of the thyroid gland ) has been reported for chronic exposure, reflecting the ability of thiourea to interfere with iodide uptake.
28.
Most preparations of episulfides utilize a two-step method, converting an olefin to an epoxide before its conversion to the episulfide using either thiocyanate or thiourea.
29.
Jacobsen's thiourea catalyst performs an enantioselective aza-MBH reaction, for example ( 25-49 % yield, 87-99 % ee ).
30.
In going from urea to thiourea to selenourea the double bond is more delocalized and longer, while the C-N ? bond is stronger and shorter.
