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首页> 外文期刊>Chemistry: A European journal >Diastereo- and enantioselective intramolecular [2+2] Photocycloaddition reactions of 3-(ω'-alkenyl)- and 3-(ω'-alkenyloxy)-Substituted 5,6-Dihydro-1H-pyridin-2-Ones
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Diastereo- and enantioselective intramolecular [2+2] Photocycloaddition reactions of 3-(ω'-alkenyl)- and 3-(ω'-alkenyloxy)-Substituted 5,6-Dihydro-1H-pyridin-2-Ones

机译：3-（ω'-烯基）-和3-（ω'-烯氧基）-取代的5,6-二氢-1H-吡啶-2-酮的非对映和对映选择性分子内[2 + 2]光环加成反应

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Abstract: 3-(ω'-Alkenyl)-substituted 5,6-dihydro-1H-pyridin-2-ones 2-4 were prepared as photocycloaddition precursors either by cross-coupling from 3-iodo-5,6-dihydro-1H-pyridin-2one (8) or-more favorably-from the corresponding α-(ωalkenyl)-substituted δ-valerolactams 9-11 by a selenylation/elimination sequence (56-62% overall yield). 3-(ω'- Alkenyloxy)-substituted 5,6-dihydro-1H-pyridin-2-ones 5 and 6 were accessible in 43 and 37% overall yield from 3-diazopiperidin-2one (15) by an ααa-chloroselenylation reaction at the 3-position followed by nucleophilic displacement of a chloride ion with an ω-alkenolate and oxidative elimination of selenoxide. Upon irradiation at λ = 254 nm, the precursor compounds underwent a clean intramolecular [2+2] photocycloaddition reaction. Substrates 2 and 5, tethered by a twoatom chain, exclusively delivered the respective crossed products 19 and 20, and substrates 3, 5, and 6, tethered by longer chains, gave the straight products 21-23. The completely regio- and diastereoselective photocycloaddition reactions proceeded in 63-83% yield. Irradiation in the presence of the chiral templates (-)-1 and (+)-31 at -75°C in toluene rendered the reactions enantioselective with selectivities varying between 40 and 85% ee. Truncated template rac-31 was prepared as a noranalogue of the well-established template 1 in eight steps and 56% yield from the Kemp triacid (24). Subsequent resolution delivered the enantiomerically pure templates (-)-31 and (+)-31. The outcome of the reactions is compared to the results achieved with 4-substituted 5,6-dihydro-1H-pyridin-2ones and quinolones.
机译：摘要：通过与3-碘-5,6-二氢-1H交叉偶联制备3-（ω'-烯基）取代的5,6-二氢-1H-吡啶-2-酮2-4作为光环加成前体。通过硒化/消除序列从相应的α-（ω烯基）取代的δ-戊内酰胺9-11-或更优选-吡啶-2-酮（8-62％的总产率）。通过ααa-氯硒基化反应，可从3-重氮哌啶-2-酮（15）以3-43％和37％的总产率获得3-（ω'-烯氧基）-取代的5,6-二氢-1H-吡啶-2-酮5和6。在3-位上，随后用ω-链烯酸酯进行氯离子的亲核置换并氧化消除亚硒酸酯。在λ= 254 nm照射后，前体化合物进行了干净的分子内[2 + 2]光环加成反应。通过双原子链束缚的基底2和5分别输送了各自的交叉产物19和20，通过较长链束缚的基底3、5和6给出了直链产物21-23。完全区域和非对映选择性的光环加成反应以63-83％的收率进行。在-75℃下在甲苯中在手性模板（-）-1和（+）-31的存在下进行辐照，使反应对映选择性，选择性在40％至85％ee之间变化。截短的模板rac-31通过8个步骤制备为成熟模板1的noalalogue，肯普三酸的产率为56％（24）。随后的拆分提供了对映体纯的模板（-）-31和（+）-31。将反应的结果与4-取代的5，6-二氢-1H-吡啶-2酮和喹诺酮所获得的结果进行比较。

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