EXTREMELY FACILE LIGAND-EXCHANGE AND DISPROPORTIONATION REACTIONS OF DIARYL SULFOXIDES, SELENOXIDES, AND TRIARYLPHOSPHINE OXIDES WITH ORGANOLITHIUM AND GRIGNARD-REAGENTS
EXTREMELY FACILE LIGAND-EXCHANGE AND DISPROPORTIONATION REACTIONS OF DIARYL SULFOXIDES, SELENOXIDES, AND TRIARYLPHOSPHINE OXIDES WITH ORGANOLITHIUM AND GRIGNARD-REAGENTS
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DOI：
10.1021/jo00022a024
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发表时间：
1991-10-25
影响因子：
3.6
通讯作者：
FUJIHARA, H
中科院分区：
文献类型：
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作者：
FURUKAWA, N;OGAWA, S;FUJIHARA, H
二芳基亚砜在-95 ℃下用有机锂试剂处理后发生异常快速的配体交换反应。 光学纯的苯基对甲苯基亚砜（4 b）与有机锂试剂在-20 ℃至-95 ℃范围内反应，得到容易的配体交换和纯化产物，即，二苯基亚砜（7）、回收的4 B和二-对甲苯基亚砜（8），定量产率的统计比为1：2：1，回收的4 B完全外消旋化。 在仅使用二芳基硒氧化物和三芳基膦氧化物的类似反应中观察到这种容易的配体交换。 O-18标记的苯基对甲苯基亚砜（4c）与有机锂试剂的反应，在没有O-18混杂的情况下，以统计比例生成产物，表明在低温下仅发生C-S键断裂。 有人建议，发生的配体交换反应的亲核攻击由有机锂试剂在亚磺酰基硫原子，得到σ-硫烷作为一个中间体，迅速崩溃。 这些结果表明，用强碱处理芳香族亚砜、氧化硒和氧化膦时应谨慎。
Diaryl sulfoxides undergo unusually rapid ligand-exchange reaction upon treatment with organolithium reagents at -95-degrees-C. Optically pure phenyl p-tolyl sulfoxide (4b) reacted with organolithium reagents at the range from -20 to -95-degrees-C to give facile ligand-exchange and disproportionation products, i.e., diphenyl sulfoxide (7), recovered 4b, and di-p-tolyl sulfoxide (8) in a statistical ratio of 1:2:1 in quantitative yields, and the recovered 4b was completely racemized. This facile ligand exchange was observed in the similar reactions using only diaryl selenoxides and triarylphosphine oxides. The reactions of O-18-labeled phenyl p-tolyl sulfoxide (4c) with organolithium reagents gave products in a statistical ratio without O-18 scrambling, indicating that only the C-S bond cleavage took place under low temperature. It is suggested that the ligand exchange reactions occur by the nucleophilic attack by organolithium reagent at the sulfinyl sulfur atom, giving sigma-sulfurane as an intermediate that collapses rapidly. These results suggest that the treatment of arylic sulfoxides, selenoxides, and phosphine oxides with strong bases should be effected with caution.