192370-87-9Relevant academic research and scientific papers
Umpolung of carbon-sulfur bonds. Novel synthesis of substituted allenes from propargylic dithioacetals
Tseng, Hsian-Rong,Lee, Chin-Fa,Yang, Lian-Ming,Luh, Tien-Yau
, p. 8582 - 8587 (2007/10/03)
Umpolung of the carbon-sulfur bonds can be achieved by treatment of propargylic dithioacetals 1 with organocuprates. The organocopper intermediates 3 gave the corresponding allenyl thioethers 4 upon protonolysis. When alkyl halides were used, propargylic thioethers 5 were obtained exclusively. Transmetalation of organocopper intermediates 3 with ZnBr2 followed by Pd(PPh3)4-catalyzed coupling with vinylic or aryl halides afforded the corresponding allenyl thioethers 4. Either 4 or 5 reacted with Grignard reagents in the presence of NiCl2(dppf) to yield the corresponding allenes 9 or 10, respectively. The overall reaction can be considered to use 1 as allene-1,3-zwitterion synthons. The relative reactivities of a propargylic ether versus a propargylic dithioacetal toward an organocopper reagent were compared. The sulfur moiety apparently has higher reactivity toward the copper reagent.
