Alkylations of (R,R)-2-t-Butyl-6-methyl-1,3-dioxan-4-ones which are not Possible with Lithium Amides may be Achieved with a Schwesinger P4 Base
Alkylations of (R,R)-2-t-Butyl-6-methyl-1,3-dioxan-4-ones which are not Possible with Lithium Amides may be Achieved with a Schwesinger P4 Base
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(R,R)-2-t-丁基-6-甲基-1,3-二恶烷-4-酮的烷基化（用氨基锂不可能实现）可以用 Schwesinger P4 碱实现
DOI：
10.1002/cber.19911240822
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
D. Seebach
中科院分区：
文献类型：
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作者：
T. Pietzonka;D. Seebach
在标题中指定的二氧杂环己酮的烯醇化物A，当用锂酰胺碱生成时，只能用高反应性亲电试剂烷基化，并且只能烷基化一次。使用Schwesinger的t-Bu-P4碱（一种非常强的所谓中性碱，含有能够在共轭P4 H+阳离子中携带正电荷的4P和13 N原子），二氧杂环己酮1甚至可以用碘丁烷进行双烷基化（产物16、17）。5，6-二甲基-和5-苄基-6-甲基二氧杂环己酮2和3可以非对映选择性地烷基化，在C（5）处形成季中心（产物4，8-14）。在一种情况下，通过转化为β-内酯6和烯烃7来确定所获得的产物4的构型（必须修改先前的作业）。甚至2，5，6，6-四烷基取代的二氧杂环己酮19也可以进一步烷基化（20 + 21）。五种新的烷基化产物水解为母体3-羟基-羧酸5，22 - 25。与固有的不稳定的烯醇化物和P411+抗衡离子实现的巨大的反应性进行了讨论。
Enolates A of the dioxanones specified in the title, when generated with lithium amide bases, can only be alkylated with highly reactive electrophiles, and only once. With Schwesinger's t-Bu-P 4 base (a very strong, so-called neutral base, containing 4P and 13N atoms capable of bearing a positive charge in the conjugate P4H+ cation) the dioxanone 1 can be doubly alkylated even with iodobutane (products 16, 17). The 5,6-dimethyl- and 5-benzyl-6-methyldioxanone 2 and 3 can be alkylated diastereoselectively with the formation of quaternary centers at C(5) (products 4, 8—14). In one case, the configuration of the product 4 obtained was determined by conversion to a β-lactone 6 and an olefin 7 (a previous assignment had to be revised). Even the 2,5,6,6-tetraalkyl-substituted dioxanone 19 could be further alkylated ( 20 + 21). Five of the new alkylation products were hydrolyzed to the parent 3-hydroxy-carboxylic acids 5, 22 — 25. The enormous reactivities achieved with the inherently labile enolates and the P411+ counterions are discussed.