Zade Sanjio S, Panda Snigdha, Singh Harkesh B, Sunoj Raghavan B, Butcher Ray J
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.
J Org Chem. 2005 Apr 29;70(9):3693-704. doi: 10.1021/jo0478656.
[structure: see text] The synthesis and characterization of a series of low-valent organoselenium compounds derived from 1-bromo-4-tert-butyl-2,6-di(formyl)benzene (22) is described. The synthesis of diselenide 25 was achieved by the lithiation route whereas bis(4-tert-butyl-2,6-di(formyl)phenyl) diselenide (26) was synthesized by treating 22 with disodium diselenide. A series of monoselenides (27, 28, and 29) was obtained by facile nucleophilic substitution of bromine in 22, using the corresponding selenolates as nucleophiles. The halogenation reactions of bis(4-tert-butyl-2,6-di(formyl)phenyl) diselenide (26) did not afford the corresponding selenenyl halides but resulted in the isolation of an unexpected cyclic selenenate ester 34 as a product. The selenide 32 was synthesized by the treatment of dimethoxymethyl diselenide with trilithiated 2-bromo-5-tert-butyl-N,N'-di(phenyl)isophthalamide. The existence of potential Se...O intramolecular nonbonding interactions was examined by IR, (1)H, and (77)Se NMR spectroscopy, X-ray crystallography, and computational studies. The X-ray crystal structures of 26 and 27, having two ortho formyl groups, reveal the absence of any Se...O interactions. However, the Se...O interactions were observed in the selenenate ester 34 where one of the formyl groups has been utilized for the selenenate ring formation. The crystal structures of 26 and 27 exhibited intermolecular short-range C-H...Se interactions (hydrogen bonding). Although there are four heteroatoms in carbamoyl moieties ortho to selenium capable of forming a five-membered ring on intramolecular coordination, no such intramolecular Se...X (X = N, O) interaction was observed in the crystal structure of 32. The density functional theory calculations at the B3LYP/6-31G* level predicted that for all the diformyl systems (47a-c, 48a-c), the anti,anti conformer (when both formyl oxygen atoms point away from the selenium) is more stable. This preference was found to be reversed in the monoformyl-substituted systems (50a,b, 51a,b), where the syn conformer (when formyl oxygen is near the selenium) is energetically more favorable than the anti conformer.
[结构：见正文] 描述了一系列由1-溴-4-叔丁基-2,6-二（甲酰基）苯（22）衍生的低价有机硒化合物的合成与表征。二硒化物25通过锂化路线合成，而双（4-叔丁基-2,6-二（甲酰基）苯基）二硒化物（26）通过用二硒化二钠处理22合成。通过使用相应的硒醇盐作为亲核试剂，对22中的溴进行简便的亲核取代，得到了一系列单硒化物（27、28和29）。双（4-叔丁基-2,6-二（甲酰基）苯基）二硒化物（26）的卤化反应没有得到相应的亚硒酰卤，而是分离出了一种意想不到的环状亚硒酸酯34作为产物。硒化物32通过用三锂化的2-溴-5-叔丁基-N,N'-二（苯基）间苯二甲酰胺处理二甲氧基甲基二硒化物合成。通过红外光谱、（1）H和（77）Se核磁共振光谱、X射线晶体学和计算研究考察了潜在的Se...O分子内非键相互作用的存在。具有两个邻位甲酰基的26和27的X射线晶体结构显示不存在任何Se...O相互作用。然而，在亚硒酸酯34中观察到了Se...O相互作用，其中一个甲酰基已用于形成亚硒酸酯环。26和27的晶体结构表现出分子间短程C-H...Se相互作用（氢键）。尽管在硒原子邻位的氨基甲酰基部分有四个能够通过分子内配位形成五元环的杂原子，但在32的晶体结构中未观察到这种分子内Se...X（X = N，O）相互作用。在B3LYP/6-31G*水平的密度泛函理论计算预测，对于所有二甲酰基体系（47a-c，48a-c），反，反构象体（当两个甲酰基氧原子都远离硒时）更稳定。发现在单甲酰基取代体系（50a,b，51a,b）中这种偏好相反，其中顺式构象体（当甲酰基氧靠近硒时）在能量上比反式构象体更有利。
