2-Lithio-3-methoxy-1,3-dimethylcyclopentene: A Synthetic Equivalent of 2-Lithio-1,3-dimethylcyclopentadiene and Useful Synthon for 6-Alkyl-1,4-dimethylfulvenes and<i>ansa</i>-Metallocene Complexes
作者:Bun Yeoul Lee、Young Chul Won、Ui Gab Joung、Eun Sook Cho、Hyosun Lee、Young-Whan Park、Kwang Ho Song
DOI:10.1055/s-2004-822324
日期:——
2-Bromo-3-methoxy-1,3-dimethylcyclopentene (3) is synthesized in 85% yield in 80 g scale by 1,2-addition of MeLi to 2-bromo-3-methyl-2-cyclopenten-1-one and subsequent in situ treatment of MeI. Addition of n-BuLi to the bromo-compound 3 in Et2O affords 2-lithio-3-methoxy-1,3-dimethylcyclopentene (1). Successive addition of RCHO [R = CH3, (CH2)2CH3, CH(CH3)2, C(CH3)3, H] and MeI to the lithium compound and aqueous acidic work-up provide cyclopentadiene compounds, 2-[CHR(OMe)]-1,3-Me2C5H3 in 60-84% yields. Treatment of the cyclopentadienes with NaH or KH in pentane affords 1,4,6-trimethylfulvene, 6-n-propyl-1,4-dimethylfulvene, 6-isopropyl-1,4-dimethylfulvene, 6-tert-butyl-1,4-dimethylfulvene and 1,4-dimethylfulvene in 67-83% yields. Ligand for an ansa-metallocene complex, CH2C(1,3-Me2Cp)2ZrCl2, can be shortly afforded in 64% yield by reacting the lithium compound 1 with the newly synthesized 1,4-dimethylfulvene.
2-溴-3-甲氧基-1,3-二甲基环戊烯(3)通过MeLi对2-溴-3-甲基-2-环戊烯-1-酮的1,2-加成反应,在80克规模下合成,收率为85%。随后对MeI的原位处理。将n-BuLi加入溴化合物3的乙醚溶液中,得到2-锂代-3-甲氧基-1,3-二甲基环戊烯(1)。连续将RCHO [R = CH3, (CH2)2CH3, CH(CH3)2, C(CH3)3, H] 和MeI添加到锂化合物中,经过酸性水洗处理,得到环戊二烯化合物2-[CHR(OMe)]-1,3-Me2C5H3,收率为60%-84%。用NaH或KH对环戊二烯进行处理,得到1,4,6-三甲基富烯、6-n-丙基-1,4-二甲基富烯、6-异丙基-1,4-二甲基富烯、6-叔丁基-1,4-二甲基富烯和1,4-二甲基富烯,收率为67%-83%。通过将锂化合物1与新合成的1,4-二甲基富烯反应,可以短时间内以64%的收率合成ansa-金属烯复合物的配体CH2C(1,3-Me2Cp)2ZrCl2。