Styrene hydroaminoalkylation with primary alkylamines
Styrene hydroaminoalkylation with primary alkylamines
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苯乙烯与伯烷基胺的氢氨基烷基化
DOI：
10.1016/j.trechm.2022.01.001
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发表时间：
2022
影响因子：
15.7
通讯作者：
Grayson J
中科院分区：
文献类型：
--
作者：
Grayson J
烯烃的氢氨烷基化（HAA）是合成α-烷基化胺的最有吸引力的方法之一，非亲电烯烃的分子间氢氨烷基化以仲胺和叔胺为底物已经取得了令人瞩目的进展。我们最近开发了一种通用的催化解决方案，用于HAA与未保护的伯烷基胺使用的有机光氧化还原催化和氢原子转移（HAT）catalysts.REACTION机制我们的HAA反应偶联电子无偏苯乙烯与未保护的伯烷基胺。催化循环从3DPA 2FBN（“PC”）的光激发开始（步骤1），然后通过PC*[Ep/2（N3·/N3 0）=+0.87V vs饱和甘汞电极（SCE）]氧化叠氮离子[Ep/2（N3·/N3 0）=+0.87V vs饱和甘汞电极（SCE）]产生叠氮基自由基N3·（步骤2）。该还原性淬灭步骤得到Stern-Volmer分析的支持。亲电N3·物种从烷基胺的α-C-H键上不可逆地夺取一个氢原子[键离解能（BDE）= 89-91±2 kcal mol-1]，得到亲核α-氨基自由基和叠氮酸（HN 3）（步骤3）。然后，该自由基与苯乙烯加成（步骤4），形成苄基自由基[E1/2（·CH 2 Ph/OCH 2 Ph）=-1.43 V vs. SCE]。通过PC·-[E½（PC/PC·-）=-1.92 V vs. SCE]进行单电子转移（SET）还原，得到相应的碳负离子，然后从HN 3（在DMSO中pKa= 7.9）进行质子转移（步骤6），得到γ-芳基胺产物，并再生两种催化剂。产物形成的量子产率为0.31，但这并不排除存在一条以H-N3（BDE= 93 kcal mol-1）到苄基自由基（PhCH 2 Me的BDE = 85.4±1.5 kcal mol-1）的HAT为特征的短固有链的可能性。动力学分析发现，在光催化剂和叠氮离子的反应是零级，在光子限制制度的操作一致。对烷基胺的零级依赖性和苯乙烯中的一级行为表明，转化率限制步骤（TLS）是自由基加成到烯烃（步骤4）或催化剂再生（步骤5）。
ORIGIN Hydroaminoalkylation (HAA) of alkenes is one of the most appealing methods for the construction of α-alkylated amines, and impressive advances in intermolecular HAA of nonelectrophilic alkenes have been made for secondary and tertiary alkylamine substrates. We recently developed a general catalytic solution for HAA with unprotected primary alkylamines using a combination of organophotoredox catalysis and hydrogen atom transfer (HAT) catalysis.REACTION MECHANISM Our HAA reaction couples electronically unbiased styrenes with unprotected primary alkylamines. The catalytic cycle begins with photoexcitation of 3DPA2FBN (‘PC’)(step 1), then oxidation of azide ion [Ep/2 (N3•/N3 0)=+ 0.87 V versus saturated calomel electrode (SCE)] by PC*[E½ (PC*/PC•–)=+ 0.92 V versus SCE] to generate azidyl radical, N3•(step 2). This reductive quenching step is supported by Stern–Volmer analysis. The electrophilic N3• species irreversibly abstracts a hydrogen atom from the α-C–H bond of the alkylamine [bond dissociation energy (BDE)= 89–91±2 kcal mol–1] giving a nucleophilic α-amino radical and hydrazoic acid (HN3)(step 3). This radical then adds to the styrene (step 4), forming a benzylic radical [E½ (• CH2Ph/0CH2Ph)=–1.43 V versus SCE]. Single electron transfer (SET) reduction by PC•–[E½ (PC/PC•–)=–1.92 V versus SCE] delivers the corresponding carbanion, followed by proton transfer from HN3 (pKa= 7.9 in DMSO)(step 6) to give the γ-aryl amine product and regenerate both catalysts. A quantum yield for product formation of 0.31 does not exclude the possibility of a short innate chain featuring HAT from H–N3 (BDE= 93 kcal mol–1) to the benzylic radical (BDE for PhCH2Me= 85.4±1.5 kcal mol–1). Kinetic analysis found that the reaction is zero order in photocatalyst and azide ion, consistent with operation in a photon-limited regime. A zero order dependence on alkylamine and first order behaviour in styrene suggests that the turnover-limiting step (TLS) is either radical addition to the alkene (step 4) or catalyst regeneration (step 5).
胺与烯烃的自由基加成1
影响因子：
15
作者：
W. Urry;O. O. Juveland
通讯作者：
O. O. Juveland