Categories: C=C Bond Formation >
Synthesis of various unsaturated compounds
A zinc carbenoid-mediated chain extension of β-dicarbonyl compounds provides access to α,β-unsaturated-γ-keto esters and amides with complete E selectivity via an intermediate zinc enolate, which is treated sequentially with iodine and DBU.
M. D. Ronsheim, C. K Zercher, J. Org. Chem., 2003, 68, 4535-4538.
Among the reported examples of new reactivity of the hypervalent iodine reagent DMP (Dess-Martin periodinane) are the one-step oxidation of secondary amides to imides and N-acyl vinylogous carbamates or ureas and the direct oxidation of benzylic and related primary amines to the corresponding nitriles.
K. C. Nicolaou, C. J. N. Mathison, Angew. Chem. Int. Ed., 2005, 44, 5992-5997.
Reaction of aryl nitriles with potassium ethyl malonate in the presence of zinc chloride and a catalytic amount of Hünig's base provided β-amino acrylates in moderate to good yield. Compared to the classical Blaise reaction, this reaction is safer, devoid of lachrymatory reagent, and is possible with less zinc chloride.
J. H. Lee, B. S. Choi, J. H. Chang, H. B. Lee, J.-Y. Yoon, J. Lee, H. Shin, J. Org. Chem., 2007, 72, 10261-10263.
The combination of Mo and cationic Au catalysts dramatically accelerated the rearrangement of diverse propargyl alcohols to yield α,β-unsaturated compounds under mild conditions, and high product yields. A practical application to the highly challenging primary propargyl alcohols and the N-alkynyl amides is achieved.
M. Egi, Y. Yamaguchi, N. Fujiwara, S. Akai, Org. Lett., 2008, 10, 1867-1870.
A highly stereoselective synthesis of aromatic α,β-unsaturated amides was achieved by treatment of aromatic α,β-epoxyamides with samarium diiodide. α,β-epoxyamides are easily prepared by the reaction of enolates derived from α-chloroamides with carbonyl compounds at -78°C.
J. M. Concellón, E. Bardales, J. Org. Chem., 2003, 5, 9492-9295.
The in situ generated Blaise reaction intermediate, a zinc bromide complex of β-enaminoester, reacts with various alkynes under mild conditions to afford α-vinylated β-enaminoesters in good to excellent yields.
Y. S. Chun, Y. O. Ko, H. Shin, S.-g. Lee, Org. Lett., 2009, 11, 3414-3417.