Highly <i>Z</i>-selective synthesis of 1,3-oxathiol-2-ylidenes and 4-methylene-oxazolidine-2-thiones <i>via</i> atom-specific 5-<i>exo-dig</i> cyclization of propargyl alcohol with isothiocyanate
作者:S. Antony Savarimuthu、D. G. Leo Prakash、S. Augustine Thomas、Thirumanavelan Gandhi、Mrinal K. Bera
DOI:10.1039/d0ob00083c
日期:——
internal propargyl alcohol to produce (Z)-1,3-oxathiol-2-ylidenes and (Z)-N-(Z)-4-ethylidene-1,3-oxathiolan-2-ylidenes from secondary and primary propargyl alcohols, respectively. The formation of high Z-selectivity in the imine motif and alkene is the highlight of this new method as multiple selectivities over C[double bond, length as m-dash]N and C[double bond, length as m-dash]C in a single system are synthetically
DBU介导的异硫氰酸酯和炔丙醇的5-exo-dig环化反应可形成有价值的杂环化合物。发现异硫氰酸酯的亲核性的不同模式(S-选择性或N-选择性)取决于炔丙醇的取代模式。对末端炔丙醇和异硫氰酸酯进行N-亲核攻击,得到3-取代的4-亚甲基恶唑烷-2-硫酮。相反,观察到内部炔丙醇的独家S亲核环化反应产生(Z)-1,3-氧杂硫醇-2-亚烷基和(Z)-N-(Z)-4-亚乙基-1,3-氧杂硫杂环戊烷-分别来自仲和伯炔丙醇的2-亚烷基。在亚胺基序和烯烃中高Z选择性的形成是这种新方法的亮点,因为在C [双键,在单个系统中,如m-N和C双键的长度,如m-C的长度在合成上是非常具有挑战性的。亚胺和烯烃中的Z-选择性可以分别归因于电子和空间因素。