Novel synthesis of phenol derivatives by palladium-catalyzed cyclocarbonylation of 2,4-pentadienyl acetates
摘要:
Phenyl acetates were selectively obtained in good yields by cyclocarbonylation of 2,4-pentadienyl acetates in the presence of NEt3, Ac2O, and a catalytic amount of palladium complexes such as PdCl2(PPh3)2 at 120-140-degrees-C under 50 atm of CO. No five-membered ring products were observed. A platinum complex PtCl2(PPh3)2 was also effective as a catalyst. The reaction of 5-phenyl-2,4-pentadienyl bromide with M(CO)(PPh3)3 (M = Pd or Pt) under CO gave the corresponding 6-phenyl-3, 5-hexadienoyl complexes in a high yield, which in turn afforded 2-acetoxybiphenyl in 41-51% yield on heating to 160-degrees-C under 50 atm of CO in the presence of NEt3 and Ac2O. Similar 3,5-hexadienoyl complexes are proposed to be intermediates in the catalytic cyclocarbonylation of 2,4-pentadienyl acetates. On the other hand, PdCl2(PPh3)2-catalyzed carbonylation of o-(bromomethyl)(1-alkenyl)-benzenes in the presence of NEt3 and Ac2O gave 2-naphthyl acetates in moderate yields, while the reaction in the absence of Ac2O gave five-membered ring products such as 2-indanones or a tricyclic lactone by incorporation of one or two CO molecules, respectively.
Cobalt-Catalyzed Diastereo- and Enantioselective Reductive Allyl Additions to Aldehydes with Allylic Alcohol Derivatives via Allyl Radical Intermediates
enantioenriched homoallylic alcohols with a remarkably broad scope of allyl groups that can be introduced. Mechanistic studies indicated that allyl radical intermediates were involved in this process. These new discoveries establish a new strategy for development of enantioselective transformations through capture of radicals by chiral Co complexes, pushing forward the frontier of Co complexes for enantioselective
An improved synthesis of gamma-hydroxybutenolides 1a-d was achieved via crossed aldolcondensation between aldehydes 2a-d and the protected gamma-hydroxy-beta-methylbutenolides 3 or 4 using the bulky Lewis acid, aluminumtris(2,6-diphenylphenoxide) (ATPH). Using this same methodology, the gamma-hydroxybutenolides 17a-d having various heteroaromatic rings were synthesized and their anti-tumor activities
A selective copper (Cu)-catalyzed C–S bond direct cross-coupling of thiols with 5-arylpenta-2,4-dienoic acid ethyl ester was developed. Notably, various biologically active 5-phenyl-3-phenylsulfanylpenta-2,4-dienoic acid ethyl ester derivatives were efficiently synthesized under moderate conditions. Finally, a plausible Cu(I)/Cu(III) reaction mechanism was proposed.
开发了选择性铜 (Cu) 催化的 C-S 键直接交叉偶联硫醇与 5-arylpenta-2,4-二烯酸乙酯。值得注意的是,各种具有生物活性的 5-苯基-3-苯基硫烷基五-2,4-二烯酸乙酯衍生物在温和条件下被高效合成。最后,提出了一种似是而非的Cu( I )/Cu( III )反应机理。
Stereoselective synthesis of naturally occurring unsaturated amide alkaloids by a modified RambergBäcklund reaction
A convenient and rapid approach for the synthesis of naturally occurring unsaturated amide alkaloids 1a1n by the recently developed one-flask RambergBacklund reaction is described. The starting material was alcohol 3, which was transformed into thiolacetate 4 using the Mitsunobu reaction. In situ cleavage of acetyl moiety of 4, followed by alkylation of the resulting thiol with appropriate chloroacetamide
Silver‐Catalyzed Olefination of Aryl Aldehydes Using Propiolates
作者:Rina Raju Manwar、Rengarajan Balamurugan
DOI:10.1002/chem.202401905
日期:2024.8.27
demonstrated as olefinating agents in the silver-catalyzed olefination of aryl and cinnamyl aldehydes to make α,β- and α,β,γ,δ-unsaturated esters with excellent E-selectivity. Trimethyl orthoformate plays a dual role by generating nucleophilic allenolate from propiolate and more electrophilic oxocarbenium ion fromaldehyde to effect the reaction.