Thiourea allylic amination

Like other acid chlorides and cyanogen bromide, vinyl chloroformate brings about fission of benzylic and allylic amines e.g. hydrastine is converted into the enol lactone (145).169 Normorphine and norcodeine give substituted thioureas (146) with alkyl isothiocyanates.170... 

The cycHc urea moiety provides structural rigidity as well as hydrogen-bonding possibihties similar to those of the imidazoles described above. The corresponding 2-imidazolones have been prepared on a soHd phase by tandem aminoacylation of a resin-bound allylic amine with an isocyanate followed by intramolecular Michael addition [73]. However, due to the paucity of data presented on the characterized compounds and the brief experimental procedure, this synthesis is not discussed in detail. Access to cyclic ureas or thioureas has also been obtained by reaction with carbonyl- or thiocarbonyldiimidazole through a cyclo-release mechanism [74—76]. 1,3-Dihydroimidazolones have been obtained by treatment of ureido acetals with TFA and subsequent conversion in an intramolecular cyclization via an N-acyliminium ion [77]. 

Based on the catalytic double activation machinery concept (tertiary phosphines/ thiourea catalyst 56), Shi and co-workers [124] were able to achieve the allylic amination of MBH acetates with phthalimides in good yields and selectivities (Scheme 11.43). Higher reactivity and enantioselectivity were observed when 25 mol% of the catalyst, 1,2-dichlorobenzene as a solvent to increase the solubility... 

SCHEME 11.43. Chiral bifunctional thiourea-phosphane-catalyzed allylic amination of MBH acetates and carbonates with phthalimide. 

Bridged bicyclic tertiary allylic amines aza-norbornene and isoquinuclidene have been reported to add to isocyanates, isothiocyanates, and in s/tM-generated carbodiimides to form zwitterionic intermediates that undergo 1,3-diaza-Claisen rearrangements to ureas, thioureas, and guanidines, respectively (Scheme 26) ... 

In 2009, the Jorgensen group developed the organocatalytic asymmetric addition of P-keto-benzothiazole-sulfones to N-Boc aromatic imines based on the thiourea organocatalyst 61 and using as solvent, unusually, propionitrile (Scheme 29.33) [70]. The reaction proceeds with moderate yields, and stereoselectivities from moderate to excellent. The initially formed adducts 62 were easily transformed into different types of protected amines like the allylic amines 63, or P-amino ketones 64 and 65. 

Berkessel and co-workers have demonstrated the utility of the bifunctional cyclohexane-diamine catalysts in the dynamic kinetic resolution of azalactones (Schemes 60 and 61) [111, 112]. The authors proposed that the urea/thiourea moiety of the catalyst coordinates and activates the electrophilic azlactone. The allyl alcohol nucleophilicity is increased due to the Brpnsted base interaction with the tertiary amine of the catalyst. 

In 2005, Wang and coworkers reported a new bifunctional binaphthyl-derived amine thiourea 16 as an efficient organocatalyst for the Morita-Baylis-Hillman reaction of cyclohexenone with aliphatic, aromatic and sterically hindered aldehydes. The design of the catalyst follows Takemoto s design of a bifunctional motif. This catalytic protocol provided access to useful chiral allylic alcohol building blocks in high yields and high enan-tioselectivities (Scheme 19.21). 

Pyrolysis of 5-ethyl iV-disubstituted dithiocarbamates gives ethylene, CS2, and secondary amines and/or a trisubstituted thiourea and ethanethiol. NNSS -Tetrasubstituted dithiocarbamidium iodides, obtained by 5-alkylating dithiocarbamates, are in equilibrium with their precursors, and this equilibrium has been used in the conversion of allylic dithiocarbamates, particularly allylic 1-pyrrolidine-carbodithioates (147), into allylic iodides by treatment with methyl iodide bis(methylthio)methylenepyrrolidinium iodide (148) is insoluble, and it precipitates from the reaction mixture (Scheme 15). AW55 -Tetramethyldithiocarbamidium iodide (149) reacts with hydroxylamine or semicarbazide with displacement of the dimethylamino-group, but with other nucleophiles, e.g. thiosemicarbazide or... 

A bifunctional amine/thiourea catalyst gives high ee in a direct vinylogous aldol reaction of allyl ketones with isatins, giving biologically important 3-hydroxy-2-oxindoles. ... 

Based on the enantioselective Michael addition/ISOC (intramolecular silyl nitronate olefin cycloaddition)/lragmentation sequence previously developed by the group of Rodriguez [33a], Shao and coworkers proposed an extrapolation for the construction of spirooxindoles catalyzed by a bifunctional tertiary amine-thiourea catalyst XV between 4-allyl-substituted oxindoles 63 and nitrostyrenes 64 (Scheme 10.21) [33b]. After the addition of TMSCl and EtgN at -30 C, the Michael adduct underwent an ISCX3 to afford the spiro oxime derivatives 65 in very good yields (85-85%), and excellent diastereo (up to >30 1) and enantioselectivities (94-99% ee) after the treatment with TBAF. 

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