On the synthesis of β-bromohydrine ethers via intermolecular alkoxyl radical addition to bicyclo[2.2.1]heptene
作者:Jens Hartung、Nina Schneiders、Thomas Gottwald
DOI:10.1016/j.tetlet.2007.06.103
日期:2007.8
Primary, secondary, and tertiary alkoxyl radicals add exo-selectively to the olefinic π-bond in bicyclo[2.2.1]heptene to afford exo-2-alkoxybicyclo[2.2.1]hept-3-yl radicals, which are trapped with BrCCl3 preferentially from the endo face to furnish β-bromohydrine ethers in 23–67% yield.
Bond angles at thiohydroxamate oxygen in crystal structures of 3-alkoxy-5-(p-methoxyphenyl)-4-methylthiazole-2(3H)-thiones gradually increased with the size of the 3-alkoxy substituent. This effect was attributed to strain on the basis of (i) a linear free energy relationship (Taft-Dubois correlation) and (H) signal coalescence from resonances of diastereotopic CH3 groups in solution (O-cumyl substituent; DNMR). Substitution at oxygen along the sequence OR (R prim-, sec-, and tert-alkyl), CH, and OLi was reflected in a gradual decrease of N,O distances and lengthening of associated C,S bonds. The responsivity for these changes was more pronounced in the thiazole-2(3H)-thione than in the pyridine-2(1H)-thione series. (C) 2009 Elsevier Ltd. All rights reserved.