3-CUPRIO-2-PYRONE - AN EXTRAORDINARY ORGANOCOPPER REAGENT
3-CUPRIO-2-PYRONE - AN EXTRAORDINARY ORGANOCOPPER REAGENT
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DOI：
10.1021/jo00225a008
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发表时间：
1985-12-13
影响因子：
3.6
通讯作者：
WETTLAUFER, DG
中科院分区：
文献类型：
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作者：
POSNER, GH;HARRISON, W;WETTLAUFER, DG
B异位铜被用作中间体。8等式2中显示的另一对底物是苯溴和胡椒酰溴：作为一个真正不同寻常的结果，苯溴即使在25℃下长时间（12小时）也不能从3-铜-2-吡酮(1)转移吡酮，但胡椒酰溴确实在25℃下反应产生替代产物。这一结果似乎支持SN1反应模式。在探索底物对有机铜试剂I的SN2-SN1反应性的尺度时，我们发现，sn2反应性底物（方案II），如碘化甲酯、溴乙酸乙酯和杂烯丙基氯化物，甚至碘化物4和5，完全不能被吡酮取代。同样，伯同烯丙基tosylate 6，甲磺酸苄酯(7)和过量的环氧乙烷即使在强制条件下也不会从3-cu -2-pyrone(1)进行pyroone转移。通常有效的酰基亲电试剂（方案III）也不能从有机铜中吸收吡酮基团；即使是过量的苯甲酰氯也没有转化为3-苯甲酰-2-吡酮，而苯甲酰氯可以通过许多不同的有机铜试剂轻松而干净地转化为酮。令我们非常惊讶的是，方案IV中所有典型的snl反应性亲电试剂也没有与铜吡咯酮1反应。方案II-IV中的底物未能从铜吡咯酮1中转移吡咯酮，这是这种有机铜物种非凡性质的一个戏剧性和明确的指示！
B allenic copper species have been invoked as intermediates. 8 One additionally revealing pair of substrates shown in eq 2 are benzyl bromide and piperonyl bromide: as a truly extraordinary result, benzyl bromide failed to undergo pyrone transfer from 3-cuprio-2-pyrone (1) even at 25 C for a prolonged time (12 h), but piperonyl bromide did react at 25 C to produce a substitution product. This result would seem to support an SN1 pattern of reactivity. In exploring the SN2-SN1 scale of substrate reactivity toward organocopper reagent I, we have found that SN2-reactive substrates (Scheme II) such as methyl iodide, ethyl bromoacetate, and heteroallylic chlorides or even iodides 4 and 5 completely failed to undergo substitution by a pyrone group. Likewise, primary homoallylic tosylate 6, benzyl mesylate (7), and ethylene oxide in excess also did not undergo pyronetransfer from 3-cuprio-2-pyrone (1) even under forcing conditions. Normally potent acyl electrophiles (Scheme III) also failed to incorporate the pyrone group from organocopper species l; 9 even excess benzoyl chloride, which is converted easily and cleanly into ketones by many different organocopper reagents, 10 was not transformedinto 3-benzoyl-2-pyrone. To our great surprise, all of the typically SNl-reactive electrophiles in Scheme IV also did not react with cupriopyrone 1. The failure of the substrates in Schemes II-IV to undergo pyrone transfer from cupriopyrone 1 is a dramatic and unambiguous indication of the extraordinary nature of this organocopper species!