Purine derivatives R 0540Cross-Coupling Reactions of Halopurines with Aryl-and Alkyltrifluoroborates. The Scope and Limitations in the Synthesis of Modified Purines. -Optimized reaction conditions are developed for the Pd-catalyzed cross-coupling reaction of halopurines with aryltrifluoroborates. In general, alkyl-substituted (II) show poor reactivity. -(HASNIK, Z.; POHL, R.; HOCEK*, M.; Synthesis
Facile and Highly Diastereoselective Synthesis of syn-and cis-1,2-Diol Derivatives from Protected -Hydroxy Ketones. -A new and diastereoselective method for the synthesis of 1,2-diols from Tmp-protected -hydroxyketones is developed. The protecting group as the stereodirecting group induces in unhindered acyclic or cyclic ketones complete syn-or cis-diastereoselectivity with L-Selectride. For more hindered compounds LiAlH4 reveals better results. The diastereoselectivity can be rationalized for acyclic ketones by the Felkin-Anh model, whereas for cyclic substrates, attack from the face opposite to the protecting group predictably prevails with high selectivity, regardless of the substitution pattern. The free diols are obtained by reductive N-O bond cleavage of the alkoxyamine unit. -(JAHN, E.; SMRCEK, J.; POHL, R.; CISAROVA, I.; JONES, P. G.; JAHN*, U.; Eur. J. Org. Chem. 2015, 35, 7785-7798, http://dx.
Fused pyrimidine derivatives R 0515 C-Functionalization of 9-Deazapurines by Cross-Coupling Reactions. -The functionalization in positions 2, 4, and 7 is described. Interestingly, treatment of the alkyne (VII) with AlMe3 does not yield the expected isopropyl derivative but the (Z)-propenyl analogue (IX). -(BAMBUCH, V.; OTMAR*, M.; POHL, R.; MASOJIDKOVA, M.; HOLY, A.; Tetrahedron 63 (2007) 7, 1589-1601; Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech Republic; Eng.) -Jannicke 23-157
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