Potassium <i>tert</i>-Butoxide Promoted Intramolecular Arylation via a Radical Pathway
作者:Daniela Sustac Roman、Yoko Takahashi、André B. Charette
DOI:10.1021/ol201160s
日期:2011.6.17
Potassium tert-butoxide mediated intramolecular cyclization of aryl ethers, amines, and amides was efficiently performed under microwave irradiation to provide the corresponding products in high regioisomeric ratios. The reaction proceeds via single-electron transfer to initiate the formation of an arylradical, followed by a kinetically favored 5-exo-trig and subsequent ring expansion.
Diarylethenes were obtained from the corresponding ethenyl sulfones by photocatalyzed desulfonylation using UV or blue LEDs. When perylene and i-Pr2NEt were used as a photocatalyst and a sacrificing reagent, respectively, this desulfonylation proceeded smoothly to afford the desired ethenes with the functional groups such as chloro, alkoxy and heteroaromatic rings remaining untouched. The use of a flow photoreactor enabled this desulfonylation to proceed more rapidly to finish in an hour of residence time.
Oxidative Mizoroki-Heck-Type Reaction of Arylsulfonyl Hydrazides for a Highly Regio- and Stereoselective Synthesis of Polysubstituted Alkenes
作者:Fu-Lai Yang、Xian-Tao Ma、Shi-Kai Tian
DOI:10.1002/chem.201103671
日期:2012.2.6
hydrazides have been identified as synthetically useful aryl sources for the Pd(OAc)2 catalyzed oxidative Mizoroki–Heck‐type reaction under molecular oxygen to provide a convenient access to polysubstituted alkenes in a highly regio‐ and stereoselective manner (see scheme). The reaction well tolerates various functional groups such as alkoxy, halo, alcohol, carboxylic acid, ester, amide, sulfonamide, and
Unequivocal Experimental Evidence for a Unified Lithium Salt-Free Wittig Reaction Mechanism for All Phosphonium Ylide Types: Reactions with β-Heteroatom-Substituted Aldehydes Are Consistently Selective for<i>cis</i>-Oxaphosphetane-Derived Products
作者:Peter A. Byrne、Declan G. Gilheany
DOI:10.1021/ja300943z
日期:2012.6.6
erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li
Palladium‐Catalyzed Annulation of 1,2‐Diborylalkenes and ‐Arenes with 1‐Bromo‐2‐[(
<i>Z</i>
)‐2‐bromoethenyl]arenes: A Modular Approach to Multisubstituted Naphthalenes and Fused Phenanthrenes
(Z)‐1,2‐Diaryl‐1,2‐bis(pinacolatoboryl)ethenes underwent double‐cross‐coupling reactions with 1‐bromo‐2‐[(Z)‐2‐bromoethenyl]arenes in the presence of [Pd(PPh3)4] as a catalyst and 3 M aqueous Cs2CO3 as a base in THF at 80 °C. The double‐coupling reaction gave multisubstitutednaphthalenes in good to high yields. Annulation of 1,2‐bis(pinacolatoboryl)arenes with bromo(bromoethenyl)arenes in the presence
(Ž)-1,2-二芳基-1,2-双(频哪醇基硼)ethenes后行双交叉偶联反应用1-溴-2 - [(ż)-2-溴乙烯基]在[钯的存在下芳烃(在80°C下于THF中作为催化剂的PPh 3)4 ]和作为碱的3 M Cs 2 CO 3水溶液。双重偶联反应以良好或高收率得到了多取代萘。在由[Pd 2(dba)3](dba =二亚苄基丙酮)和2-二环己基膦基2',6'-二甲氧基联苯(SPhos)在相同条件下可生产高产量的稠合菲。第一次环偶联发生在溴乙烯基基团区域上。此程序适用于通过使用相应的二溴双[[ Z)-2-溴乙烯基]苯作为二硼烷基偶联伙伴的双环途径轻松合成多取代的蒽,苯并噻吩和二苯并蒽。