Alkylation Reactions at the Benzo Moiety of 2,4-Dimethoxy-3-(phenylsulfonyl)benzo[a]heptalenes - Model Compounds of Colchicinoids
作者:Samir El Rayes、Anthony Linden、Khaled Abou-Hadeed、Hans-Jürgen Hansen
DOI:10.1002/hlca.201000191
日期:2010.10
accompanied by the reductiveelimination of the X‐sulfonyl group at C(3) (Table 3). Most exciting is also the course of 2,4‐dimethoxy‐3‐(phenylsulfonyl)benzo[a]heptalenes in the presence of an excess of MeLi. After the expected exchange of MeO against Me at C(4) (Scheme 6), rearrangement takes place under formation of 4‐benzyl‐2‐methoxybenzo[a]heptalenes and concomitant loss of the sulfonyl group at C(3) (Table 4)
研究了3-(X-磺酰基)苯并[ a ]庚二烯-2,4-二醇(X = Ph,吗啉-4-基)及其二甲醚的烷基化反应。二醇在水性介质中与K 2 CO 3 / MeI形成1-甲基化苯并庚烷,但收率不超过20%(表1)。另一方面,2,4-二甲氧基苯并[ a ]庚烷可以很容易地在C(3)上用BuLi进行锂化,然后用烷基碘进行处理,从而以高收率得到3-烷基化形式(表2)。令人惊讶的是有两个当量的反应。或更多的t- BuLi,因为C(4)处的烷基化伴随着C(3)处X-磺酰基的还原消除(表3)。在过量的MeLi存在下,2,4-二甲氧基-3-(苯磺酰基)苯并[ a ]庚烷的过程也最令人兴奋。在C(4)处将MeO与Me交换后(方案6),在形成4-苄基-2-甲氧基苯并[ a ]庚烯并伴随C(3)磺酰基损失的情况下发生重排(表4)。)。在X =吗啉-4-基的情况下,不会发生重排。但是,类型E的中间体苄基阴离子(方案8)很容易与空气中的O
Reductive Elimination of Phenylsulfonyl Groups in the 3-Position of Benzo[a]heptalene-2,4-diols
作者:Mohy eldin Abdel Fattah、Samir El Rayes、El Sayed Ahmed Soliman、Anthony Linden、Khaled Abou-Hadeed、Hans-Jürgen Hansen
DOI:10.1002/hlca.200590080
日期:2005.5
3-(Phenylsulfonyl)benzo[a]heptalene-2,4-diols 1 can be desulfonylated with an excess of LiAlH4/MeLi⋅LiBr in boiling THF in good yields (Scheme 6). When the reaction is run with LiAlH4/MeLi, mainly the 3,3′-disulfides 6 of the corresponding 2,4-dihydroxybenzo[a]heptalene-3-thiols are formed after workup (Scheme 7). However, the best yields of desulfonylated products are obtained when the 2,4-dimethoxy-substituted
可以在沸腾的THF中用过量的LiAlH 4 / MeLi·LiBr将3-(苯磺酰基)苯并[ a ]庚二烯-2,4-二醇1以良好的产率脱磺酰化(方案6)。当用LiAlH 4 / MeLi进行反应时,在处理后主要形成相应的2,4-二羟基苯并[ a ]庚烯-3-硫醇的3,3'-二硫化物6(方案7)。但是,当在−7820°的THF中用过量的LiAlH 4 / TiCl 4还原2,4-二甲氧基取代的苯并[ a ]庚烷2时,可获得最佳的脱磺酰化产物收率(方案10))。尝试替代PhSO 2的组2与新鲜制备的MeONa在沸腾的THF中导致了4-的MeO组的高度选择性醚裂解,而不是脱磺酰(方案13)。