The addition of potassium enoxyborates to the chelated allyl-iron-carbene complex 1 leads to the corresponding η 4-(3E)-1,3-diene complexes 2 in fair yields. Complexes 2 can be demetalated with ceric ammonium nitrate (CAN) to give unrearranged (3E)-t-oxo-1,3-dienes 3. Prior to decomplexation, the carbonyl group can be further modified. This is demonstrated by the syntheses of the natural terpene alcohol hotrienol and of a complexed methylene-separated dienyne. Potassium enoxyborates are superior to lithium enolates as they are readily prepared in situ from a variety of aldehydes and ketones which do not form sufficiently stable lithium derivatives. In contrast to lithium enolates, only C-C coupling products derived from the "kinetic" regioisomers are formed from unsymmetrical aliphatic ketones.
将
钾酯
硼酸盐添加到螯合的烯丙基
铁碳烯复合物1中,可以在合理产率下得到相应的 η 4-(3E)-1,3-二烯复合物2。复合物2可以用
铈铵硝酸盐(CAN)去
金属化,得到未重新排列的 (3E)-t-氧基-1,3-二烯3。在去复合之前,可以进一步修饰羰基。这通过合成天然萜醇霍特里诺尔和一种复合的亚甲基分隔的二炔来证明。
钾酯
硼酸盐优于
锂烯醇盐,因为它们可以在多种不形成足够稳定的
锂衍
生物的醛和酮中原位制备。与
锂烯醇盐相比,仅从不对称脂肪族酮中形成源自“动能”区域异构体的C-C偶联产物。