.alpha.,.alpha.' Dianions of aliphatic ketones and the 1,3,5 trianion of 2,4-pentanedione: strongly nucleophilic carbonyl synthons
.alpha.,.alpha.' Dianions of aliphatic ketones and the 1,3,5 trianion of 2,4-pentanedione: strongly nucleophilic carbonyl synthons
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DOI：
10.1021/ja00526a069
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发表时间：
1980-03
影响因子：
15
通讯作者：
James S. Hubbard;T. Harris
中科院分区：
文献类型：
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作者：
James S. Hubbard;T. Harris
2110美国化学学会杂志/102：6/3月12日，980和C4-C5键与这种应变偶氮烷中的C1-N2和N3-C4键相比被充分削弱，因此通过5*的逆环过程比通过氮气挤出更可取，以获得预期的双基4(式1)。当然，不是通过5*的协同过程，而是一种逐步的机制，涉及第一个Ci-CFI键断裂以产生双自由基。无论是哪一种机理过程，偶氮烷6的热行为都是不寻常的；然而，已有少数例子报道了偶氮烷烃在加热时转化为吡唑而不是放出分子氮。与热分解相反，偶氮烷烃5在~10-4M戊烷(光谱质量)中在石英容器254和吡喃容器350 nm下直接光解得到预期的三环烯2(350 nm处99.0±0.3%和254 nm处96.0±0.3%)和双环烯1(350 nm处1.0±0.3%和254 nm处4.0±0.3%)。对照实验证实，在我们的光解条件下，1不会转化为2.10，因此，1的低产率表明，从单重态激发的偶氮烷5光挤出氮气时形成的双自由基4有效地环化成2，而不是重排成双自由基3得到1(方程1)。显然，二自由基4代表偶氮烷烃的单重态前被引态能面上的最小能量。最令人惊讶的结果出现在二苯甲酮敏化偶氮烷烃5的光解反应中，该反应是在配备300 nm灯的Rayonet反应器中进行的，在脱氧C6D6中使用~10-4M5和~10-3M二苯甲酮溶液。使用合适的K^C^O？/K2CO3水相滤光器，只允许300-330 nm的光照射样品。4经1H核磁共振确证的唯一产物为新的二氮杂环丙烷衍生物7，经燃烧分析，熔点140C dec，C111qN 2元素组成，MJE 170。波谱数据8证实了该化合物的结构归属：1H-1.85(2H，H5，m)，3.3-3.8(2，H，6，m)，3.9(1H，H9，d，Ji9=2.9 Hz)，6.7-7.2(4H，C6H4，m)，7.5(1H，H4，m)；(Ppm)123.01,125.84,127.30,127.87,137.27,147.02,156.99；IR(KBrv)v(cm“1)3050,3030,3025,2955,2921,1600,1480,1460,1442,1345,1330,1310,1230,1200,1160,1070,1005,935,920。这种物质是热不稳定的，导致复杂的产物混合物，但不产生吡唑6。
2110 Journal of the American Chemical Society/102: 6/March 12,¡ 980 and C4-C5 bonds are sufficiently weakened compared with the C1-N2 and N3-C4 bonds in this strained azoalkane that the retrocyclic process via 5* is prefered over N2 extrusion to afford theexpected diradical 4 (eq 1). Of course, instead of the concerted process via 5*, a stepwise mechanism involving first Ci-Cfi bond rupture to yield a diradical is also likely. Whichever the mechanistic course, the thermal behavior of the azoalkane 6 is unusual; however, a few examples have been reported9 in which azoalkanes transform into pyrazolesinstead of expelling molecular nitrogen on heating. In contrast to the thermolysis, direct photolysis of the azo-alkane 5 in~ 10-4 M pentane (Spectroquality) at 254 (quartz vessel) and 350 nm (Pyrex vessel) in a Rayonet reactor gave the expected tricycloalkene 2 (99.0±0.3% at 350 nm and 96.0±0.3% at 254 nm) and the bicycloalkadiene 1 (1.0±0.3% at 350 nm and 4.0±0.3% at 254 nm). Control experiments confirmed that under our photolysis conditions 1 is not trans-formed into 2.10 Consequently, the low yield of 1 suggests that the diradical 4, formed on photoextrusion of N2 from the singlet excited azoalkane 5, efficiently cyclizes into 2 rather than rearranging into diradical 3 to give 1 (eq 1). Apparently, the diradical 4 represents an energy minimum on the singlet ex-cited-state energy surface of the azoalkane. The most surprising result was observed in the benzophenone-sensitized photolysis of azoalkane 5, which was carried out in a Rayonet reactor, equipped with 300-nm lamps and employing solutions~ 10-4 M 5 and~ 10-3 M benzophenone in deaerated C6D6. Only 300-330-nm light was allowed to irradiate the sample by utilizing an appropriate K^ C^ O?/K2CO3 aqueous filter. 4 The only productthat was detected by 1H NMR was the novel diazavinylcyclopropane derivative 7, mp 140 C dec, C11 1 qN2 elementalcomposition by com-bustion analysis, mje 170. The following spectral data8 confirm the structural assignment:* H NMR (CDCI3, Me4Si)(ppm) 1.7-1.85 (2 H, H5, m), 3.3-3.8 (2, H, 6, m), 3.9 (1 H, H9, d, Ji9= 2.9 Hz), 6.7-7.2 (4 H, C6H4, m), 7.5 (1 H, H4, m); 13C NMR (CDCI3, Me4Si)(ppm) 27.24, 33.24, 46.96, 51.47, 123.01, 125.84, 127.30, 127.87, 137.27, 147.02, 156.99; IR (KBr) v (cm" 1) 3050, 3030, 3025, 2955, 2921, 1600, 1480, 1460, 1442, 1345, 1330, 1310, 1230, 1200, 1160, 1070, 1005, 935, 920. This substance is thermally labile, leading to a complex product mixture, but the pyrazole 6 is not produced.