炔烃与二氯硼烷-甲硫醚的硼氢化反应——偕-二硼和烯基硼化合物的合成和光谱特性

本文研究了在三氯化硼存在下,炔烃与二氯硼烷-甲硫醚(HCCl_2·SMe_2)的硼氢化反应。内炔烃和端炔烃与HBCl_2·SMe_2(摩尔比为1:2)在0℃反应,得到了高产率的双硼氢化产物——偕-双(二氯硼基)烷烃。在较低温度下,双硼氢化被显著地抑制。因此,在—20℃或—30℃下,内炔烃与HBCl_2·SMe_2(1.4:1)反应,定量地生成预期的烯基二氯硼烷。但在同样条件下,端炔烃既进行单硼氢化,也会经历硼氯化反应。当端炔烃在戊烷中与三氯化硼(1:1。1)反应时,高产率地得到硼氯化产物——2-氯-1-烯基二氯硼烷。各取代二氯硼烷易于醇解为相应的硼酸酯。所得化合物经IR,~1H,~(11)B,或~(13)C NMR表征。讨论了化合物的结构和它们的波谱特性之间的关系。基于化学位移,确证分子中的π-电子或孤对电子和硼原子的空ρ-轨道存在着明晰的(pp)π-相互作用。     

联吡啶配体促进铬催化炔烃的顺式硼氢化反应（英文）

报道了金属铬催化炔烃的硼氢化反应.廉价易得的三氯化铬在4,4’-二叔丁基-2,2’-联吡啶配体及单质镁的还原作用下表现出高反应活性,催化实现了频哪醇硼烷与炔烃加成的硼氢化反应,为室温条件下制备烯基硼化合物提供了一条有效的合成策略.     

含活泼次甲基的烯基硼酸酯类化合物的设计与合成

以3-溴丙炔、频哪醇硼烷和氧化吲哚或β-酮酸酯为原料,经过两步反应合成了4个含氧化吲哚官能团的烯基硼酸酯2a~2d和5个β-酮酸酯取代的烯基硼酸酯化合物3a~3e,其结构经¹HNMR,¹³CNMR和HR-MS(ESI-TOF)表征。目标化合物可作为有机合成子用于新型串联反应的开发,进而为创新药物的筛选提供新化合物。      

硼酸酯偶联剂的合成与表征

通过分子结构设计，合成了一种氮一硼内配位结构的硼酸酯偶联剂，解决了硼酸酯水解稳定性差的问题，同时分子结构中含有氨基、丁氧基等活性基团。用傅立叶变换红外光谱对硼酸酯进行了结构表征，讨论了原料配比、合成工艺等对硼酸酯收率及反应速率的影响，并通过实验确定了最佳配方及工艺。对硼酸酯的物理性能、溶解性、水解稳定性及对硼酸铝晶须的表面处理效果进行了表征。结果表明：合成的硼酸酯偶联剂由于具有氮-硼内配位作用，表现出优良的水解稳定性，并且硼酸酯偶联剂对硼酸铝晶须具有良好的表面改性效果。     

亮点介绍

无金属参与的硼化反应:从N-对甲基苯磺酰基腙合成烷基硼酸酯Angew.Chem.Int.Ed.2012,51,2493～2496有机硼化合物,包括芳基硼化合物和烷基硼化合物,在有机合成上有着重要的作用.近些年来,烷基硼化合物的偶联反应以及官能团转化反应取得了很大的进展.与此同时,烷基硼酸的生物活性研究也得到了较多的关注.目前合成烷基硼化合物主要有四种方法:一是格氏试剂或锂试剂与硼试剂反应;二是Brown硼氢化反应;三是Miyaura     

新型硼氮磷一体化阻燃剂的合成

分别以硼酸、二乙醇胺、三氯氧磷和季戊四醇为原料,经酯化反应制得中间体二乙醇胺硼酸酯（DEAB, 1）和双季戊四醇二氯磷酸酯（SPDPC, 2）; 1与2经缩聚反应合成新型集磷、氮、硼于一体的阻燃剂聚季戊四醇双磷酸酯二磷酰氯螺环二乙醇胺硼酸酯（PPSPSDB, 3）,其结构经¹H NMR, ¹³C NMR和FT-IR表征。考察了溶剂、物料比γ［n(2)：n(1)］、反应温度和反应时间对3产率的影响,结果表明：在最佳反应条件（DMF为溶剂,γ=1 ：1.2, 于120 ℃反应2 h后,于190 ℃反应2 h）下,产率93.26%。热重分析表明：3的初始分解温度为240.5 ℃, 800 ℃时残炭率为44.45%。     

锌-锂双金属化合物的合成及其在异腈酸酯硼氢化中的催化应用

有关异腈酸酯硼氢化反应的报道极其稀少,迄今为止,锌金属化合物催化的异腈酸酯硼氢化反应尚未见报道.介绍了一种结构新颖的不对称β-二亚胺锌-锂双金属化合物的合成方法,并将其作为高效催化剂成功应用于一系列带有不同官能团的异腈酸酯和频哪醇硼烷的硼氢化反应中,同时对硼氢化反应机理进行了初步探索.     

新型含硼聚芳醚酮的制备、性能及在偶氮聚芳醚酮合成中的应用

利用双酚A型聚芳醚酮与联硼酸频哪醇酯在[Ir(COD)Cl]2和4,4'-二叔丁基-2,2'-联吡啶催化下反应,制备了新型含硼酸酯双酚A型聚芳醚酮,通过控制联硼酸频哪醇酯的投入量来实现硼酸酯的定量引入.再经过高碘酸钠作用得到含硼酸双酚A型聚芳醚酮,最后,通过高效Suzuki-Miyaura反应将偶氮定量引入到聚芳醚酮主链.利用核磁共振(1H NMR)确定了聚合物的结构,利用凝胶渗透色谱(GPC)确定了聚合物的分子量,利用差示扫描量热分析(DSC)和热失重分析(TGA)研究了聚合物的热性能,利用紫外-可见光谱(UVVis)研究了偶氮聚芳醚酮的光谱学性能.     

2-二氟甲氧(硫)基吡啶-5-硼酸频哪醇酯类化合物的合成

以吡啶类化合物作为起始原料,先经二氟甲基化反应在羟基或巯基上引入二氟甲基基团,再用铱催化剂活化吡啶环的C-H并直接引入硼酸频哪醇酯基团,得到目标化合物,其产物结构经¹H NMR、¹³C NMR、MS和元素分析确证。该方法具有合成路线较短、反应条件温和、原料廉价易得以及产率较高等优点。     

铁催化酮羰基的硼化反应合成α-羟基硼酸酯

报道了一种铁催化烷基酮类化合物硼化合成三级α-羟基硼酸酯的反应,使用了可商业购买的FeBr₂作为催化剂,加入醇作为添加剂来加速反应的进行,同时避免副反应的发生.通过该方法合成了一系列三级α-羟基硼酸酯化合物,反应具有很好的底物兼容性以及官能团兼容性.该铁催化剂对于大位阻的酮类化合物的硼化反应,表现出优于铜催化的活性.同时该反应可应用于克级规模的制备,随后通过对三级α-羟基硼酸酯的C-O键进行官能化,将所得的三级α-羟基硼酸酯转化为三级烷基硼酸酯以及偕二硼、偕硅硼类化合物.     

Rhodium-Catalyzed Remote Borylation of Alkynes and Vinylboronates

Remote functionalization involving a fascinating chain-walking process has emerged as a powerful strategy for the rapid access to value-added functional molecules from readily available feedstocks. However, the scope of current methods is predominantly limited to mono- and di-substituted alkenes. The remote functionalization of multi- and heteroatom-substituted alkenes is challenging, and the use of alkynes in the chain walking is unexplored. We herein report a rhodium catalyzed remote borylation of internal alkynes, offering an unprecedented reaction mode of alkynes for the preparation of synthetically valuable 1,n-diboronates. The regioselective distal migratory hydroboration of sterically hindered tri- and tetra-substituted vinylboronates is also demonstrated to furnish various multi-boronic esters. Synthetic utilities are highlighted through the selective manipulation of the two boryl groups in products such as the regioselective cross coupling, oxidation, and amination.     

Regiocontrolled Cu(I)-catalyzed borylation of propargylic-functionalized internal alkynes

Good to excellent reactivity and regiocontrol have been achieved in the Cu(I)-catalyzed borylation of dialkyl internal alkynes with bis(pinacolato)diboron. The presence of a propargylic polar group (OH, OR, SAr, SO(2)Ar, or NHTs), in combination with PCy(3) as ligand, allowed maximizing the reactivity and site-selectivity (β to the propargylic function). DFT calculations suggest a subtle orbitalic influence from the propargylic group, matched with ligand and substrate size effects, as key factors involved in the high β-selectivity. The vinylboronates allowed the stereoselective synthesis of trisubstituted olefins, while allylic substitution of the SO(2)Py group without affecting the boronate group provided access to formal hydroboration products of unbiased dialkylalkynes.     

Monomeric Magnesium Catalyzed Alkene and Alkyne Hydroboration

In this work, two monomeric magnesium alkyl complexes ( 1 and 2 ) were prepared using bis(phosphino)carbazole framework and among them 1 has been used as a catalyst for hydroboration of alkenes and alkynes with pinacolborane (HBpin). A broad variety of aromatic and aliphatic alkenes and alkynes were efficiently reduced. Anti-Markovnikov regioselective hydroboration of alkenes and alkynes was achieved, which was confirmed by deuterium-labelling experiments. The work represents the first example of the use of magnesium in homogeneous catalytic hydroboration of alkene with broad substrate scope. Experimental mechanistic investigations and DFT calculations provided insights into the reaction mechanism. Finally, the hydroboration protocol was extended to terpenes.     

Copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids under ligand-free or both ligand-and base-free conditions

An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis(pinacolato)diboron was developed, affording b-vinylboronates as the only products in high yields. Extra hydrogen sources such as methanol are not needed in this catalytic system. This reaction could be performed successfully under ligand- and base-free conditions. It demonstrated that phenylpropiolic acids can be employed as alkyne synthons in the hydroboration reaction and exhibited good reactivity and higher selectivity than terminal alkynes.     

Theoretical mechanism for selective catalysis of ruthenium complex catalyzed hydroboration of terminal alkynes to Z‐vinylboronates

Detailed mechanism of the hydroboration of terminal alkynes catalyzed by ruthenium complex was studied using density functional theory. The calculated results suggest that the reaction proceeds in two steps: alkyne rearrangement and catalyst regeneration. Vinylboronate products with E and Z configuration are formed in this reaction. Path A forming Z‐vinylboronate is the preferred pathway. Noncovalent interaction between B? H bond and Ru centre determines the preferred pathway of the reaction. The E_gap of HOMO‐LUMO for the reactant is lowered with the assistance of ruthenium–borane complex (Ru–Cat) formation. A hypothetical control model using 1, 2‐dimethyl acetylene (internal alkyne) and styrene (terminal alkene) as the reaction substrates was designed. The calculated results suggest that the activation barrier of the rate‐determining process is too high, which make the hydroboration reaction of styrene and 1, 2‐dimethyl acetylene (CH₃C‐CCH₃) hard to occur. The results uncover the selectivity of the ruthenium complex for hydroboration of terminal alkynes. © 2014 Wiley Periodicals, Inc.     

Copper-catalyzed boration of activated alkynes. Chiral boranes via a one-pot copper-catalyzed boration and reduction protocol

Phosphine–copper(I) complexes efficiently catalyzed the mono-boration of electron-deficient alkynes in the presence of MeOH and also catalyzed conjugate reductions of alkenylboronates bearing an electron-withdrawing group. The mono-addition of bis(pinacolato)diboron to alkynes catalyzed by a copper–Xantphos complex produced vinylboronates with high regio and stereoselectivity and asymmetric reduction of the vinylboronates by a chiral copper–bisphosphine catalyst allowed the synthesis of valuable chiral boranes with high enantioselectivity. One-pot boration/asymmetric reduction of α,β-unsaturated alkynoates could be conducted with a single copper–phosphine catalyst.     

Zinc‐Catalysed Hydroboration of Terminal and Internal Alkynes

A regioselective hydroboration of alkynes has been developed by using commercially available zinc triflate as a catalyst, in the presence of catalytic amount of NaBHEt₃. The reaction tolerates a wide range of terminal alkynes having several synthetically useful functional groups and proceeds regioselectively to furnish hydroborated products in moderate to excellent yields. This system shows moderate chemoselectivity towards terminal C≡C bond over terminal and internal C=C bond and internal C≡C bond.     

Magnesium‐Catalyzed Hydroboration of Terminal and Internal Alkynes

A magnesium‐catalyzed hydroboration of alkynes providing good yields and selectivities for a wide range of terminal and symmetrical and unsymmetrical internal alkynes has been developed. The compatibility with many functional groups makes this magnesium catalyzed procedure attractive for late stage functionalization. Experimental mechanistic investigations and DFT calculations reveal insights into the reaction mechanism of the magnesium catalyzed protocol.     

Dialkylborane-Catalyzed Hydroboration of Alkynes with 1,3,2-Benzodioxaborole in Tetrahydrofuran

Dialkylborane catalyzed hydroboration of alkynes with an equimolar amount of 1,3,2-benzodioxaborole in tetrahydrofuran efficiently to provide 2-alkenyl-1,3,2-benzodioxaborole under mild reaction conditions.     

Electrochemical Hydroboration of Alkynes

Herein we reported the electrochemical hydroboration of alkynes by using B₂Pin₂ as the boron source. This unprecedented reaction manifold was applied to a broad range of alkynes, giving the hydroboration products in good to excellent yields without the need of a metal catalyst or a hydride source. This transformation relied on the possible electrochemical oxidation of an in situ formed borate. This anodic oxidation performed in an undivided cell allowed the formation of a putative boryl radical, which reacted on the alkyne.