H三 H EtMgBr,BrMg≡MgBr/ MaBr Na/NH3/110C ≡一N or nanH 2 Na/NH3/200C na=na or nanh R R OH HO OH R R R H R R OH HO OH OH OH RH H EtMgBr BrMg MgBr Na Na/NH3 or NaNH2 Na Na/NH3 or NaNH2 Na MgBr /110 oC /200 oC R' OH R OH R HO R R' OH R OH R' R OH R R HO OH R R OH