124126-31-4Relevant articles and documents
Formation of chiral C(sp3)-C(sp) bond by allylic substitution of secondary allylic picolinates and alkynyl copper reagents
Kiyotsuka, Yohei,Kobayashi, Yuichi
scheme or table, p. 7489 - 7495 (2010/01/06)
(Chemical Equation Presented) To establish allylic substitution of secondary allylic alcohol derivatives with alkynyl copper reagents, allylic esters bearing the (2-pyridine)CO2-, (2-pyrazine)CO2-, (EtO)2PO2-, C6F5CO2-, o-(Ph2P)-C6H4CO2-, MeOCO 2-, or. AcO- group were examined. First, picolinate (R 1=Me, R2=CH2OPMB) was subjected to reaction with (TMS-C≡C)2CuLi 3 LiBr at 0 °C. Although no substitution took place, MgBr2 (3 equiv) was found to promote the reaction to produce the anti SN2′ product in 93% yield with 94% regioselectivity and 99% chirality transfer. In contrast, substitution of the other esters with the copper reagent in the presence of MgBr2 were less reactive ((2-pyrazine)CO2-) or marginally reactive (other cases). Generality of the substitution using picolinates was established with five picolinates (R1=Me, Ph(CH2)2, PMBO(CH 2)3; R2=Me, CH2OPMB, CH 2OTBS, C5H11, c-C6H11) and seven alkynyl copper reagents (R3=TMS, Ph, p-TBSOC 6H4, p- and o-MeOC6H4, p-MeC 6H4, p-FC6H4), furnishing anti SN2′ products in 61-93% yields with high regioselectivity (usually >90%) and high chirality transfer (usually >95%). In addition, transformation of the products was briefly studied. 2009 American Chemical Society.
