کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5225996 | 1383564 | 2010 | 9 صفحه PDF | دانلود رایگان |
Substitution of optically active allylic picolinate, cis R1-CH(OC(O)(2-Py))CHCHR2 (R1=(CH2)2Ph, R2=CH2OTBS), with phenylcopper reagents derived from salt free PhLi (2 equiv) and CuBr·Me2S (2 and 1 equiv, respectively) was highly promoted by MgBr2 (3 equiv), producing anti SN2Ⲡproduct regio- and stereoselectively. This reagent system was proven to be general with several picolinates (R1, R2: Ph(CH2)2, PMBO(CH2)3, Me, TBSOCH2, PMBOCH2, c-Hex). Furthermore, aryl copper reagents prepared from ArLi, which was in turn prepared by Li-halogen exchange, was proven to be compatible with the substitution in the presence of larger quantity of MgBr2 than that of LiX coproduced by the exchange. Substitution was not interfered with the steric hindrance on aryl coppers (Ar: 2-MeOC6H4, 2,6-(MOMO)2-4-MeC6H2, 2,6-Me2C6H3, etc.). Similarly, stereodefined cis and trans alkenyl, furyl, and thienyl reagents gave the corresponding anti SN2Ⲡproducts efficiently.
Journal: Tetrahedron - Volume 66, Issue 3, 16 January 2010, Pages 676-684