Allylic hydroxy phosphonates and their derivatives can be interconverted by using cross metathesis with second generation Grubbs catalyst. The absolute stereochemistry of the starting phosphonate is conserved in the product. Cross metathesis reaction of the acrolein-derived phosphonate 2a yields a series of functionalized allylic hydroxy phosphonates. However, the cross metathesis reaction is often accompanied by competing dimerization and alkene migration reactions leading to a reduction in yield. The cinnamaldehyde- and crotonaldehyde-derived phosphonates 2b and 2c were also examined. In general, the metathesis reactions of phosphonates 2b and 2c are considerably slower than those for phosphonate 2a leading to mixtures. Several hydroxyl-protected derivatives of the phosphonate 2a (methyl carbonate 3a, acetate 4a, N-tosyl carbamate 5a, TBDMS 6a, and acetoacetate 7a) undergo metathesis without competing side reactions to give substituted allylic phosphonates in good to excellent yield.
Organo-phosphorus compounds S 0080 Synthesis of Nonracemic Allylic Hydroxy Phosphonates via Alkene Cross Metathesis. -The alkene cross metathesis can be applied successfully to the synthesis of various allylic hydroxy phosphonates and their hydroxy-protected derivatives. The enantiomeric excess of educts is preserved in the products. -(HE, A.; YAN, B.; THANAVARO, A.; SPILLING*, C. D.; RATH, N. P.; J. Org. Chem. 69 (2004) 25, 8643-8651; Dep. Chem. Biochem., Univ. Mo., St. Louis, MO 63121, USA; Eng.) -Jannicke 20-181
Treatment of allylic hydroxy phosphonates in aldehyde solution with mercuric trifluoroacetate, followed by the reduction of the organomercurial intermediate, afforded the cyclic acetal derivatives. The reaction displays high diastereo-and regio-selectivity. 31 P NMR studies showed the formation of an intermediate hemiacetal and rapid formation of the organomercurial upon addition of mercuric trifluoroacetate. However, the oxymercuration was reversible, and attempts to remove the excess aldehyde often led to recovery of the starting material. Fortunately, reduction of the organomercurial intermediate with sodium cyanoborohydride in the presence of the aldehyde led to more reproducible yields.
Organo-phosphorus compounds S 0080Allylic Hydroxy Phosphonates: Versatile Chiral Building Blocks. -Palladium--catalyzed reactions of allylic hydroxy phosphonates, e.g. (I), with nitrogen nucleophiles represents an efficient regio-and stereoselective pathway to βand γ-substituted amino phosphonates, e.g. (III) and (IV). In a similar manner, the rearrangement of allylic tosyl carbamates like (V) proceeds in a stereoselective manner (16th international conference on phosphorus chemistry). -(DE LA CRUZ, A.; HE, A.; THANAVARO, A.; YAN, B.; SPILLING*, C. D.; RATH, N. P.; J. Organomet. Chem. 690 (2005) 10, 2577-2592; Dep. Chem. Biochem., Univ. Mo., St. Louis, MO 63121, USA; Eng.) -Mischke 42-192
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