148601-11-0Relevant articles and documents
Stereoselective synthesis of substituted all-trans 1,3,5,7-octatetraenes by a modified Ramberg-B?cklund reaction
Cao, Xiao-Ping
, p. 1301 - 1307 (2002)
The reaction of allylic dienylic sulfone with dibromodifiuoromethane in the presence of alumina-supported KOH in dichloromethane solution results in facile rearrangement affording the corresponding all-trans 1,3,5,7-octatetraenes in excellent yields. This result shows that the double bonds of stereochemically defined allylic dienylic sulfone retain their stereochemistry and the newly formed double bond has an (E)-configurafion in the modified Rambeig-B?cklund procedure.
Cobalt-Catalyzed Diastereo- And Enantioselective Reductive Allyl Additions to Aldehydes with Allylic Alcohol Derivatives via Allyl Radical Intermediates
Wang, Lei,Wang, Lifan,Li, Mingxia,Chong, Qinglei,Meng, Fanke
, p. 12755 - 12765 (2021/08/30)
Catalytic generation of ambiphilic π-allyl-metal complexes and their utility in enantioselective transformations constitutes a powerful approach for introduction of allyl groups to a molecule. Herein an unprecedented cobalt-catalyzed highly site-, diastereo-, and enantioselective protocol for stereoselective formation of nucleophilic allyl-Co(II) complexes followed by addition to aldehydes is presented. The reaction features diastereo- and enantioconvergent conversion of easily accessible allylic alcohol derivatives to diversified 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 catalysis.
SN2″-Selective and Enantioselective Substitution with Unsaturated Organoboron Compounds and Catalyzed by a Sulfonate-Containing NHC-Cu Complex
Zhou, Yuebiao,Shi, Ying,Torker, Sebastian,Hoveyda, Amir H.
, p. 16842 - 16854 (2018/11/27)
The first broadly applicable strategy for SN2″-selective and enantioselective catalytic substitution is disclosed. Transformations are promoted by 5.0 mol% of a sulfonate-containing NHC-Cu complex (NHC = N-heterocyclic carbene), and are carried
Stereoselective synthesis of naturally occurring unsaturated amide alkaloids by a modified Ramberg-Baecklund reaction
Li, Yang,Zhang, Yu,Huang, Zhi,Cao, Xiaoping,Gao, Kun
, p. 622 - 630 (2007/10/03)
A convenient and rapid approach for the synthesis of naturally occurring unsaturated amide alkaloids 1a-1n by the recently developed one-flask Ramberg-Baecklund 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 5, provided the sulfide 6. Oxidation of sulfide 6 gave the corresponding sulfone 2. Treatment of the sulfone 2 with the dibromodifluoromethane in the presence of alumina-supported potassium hydroxide in dichloromethane solution afforded unsaturated amide alkaloids 1a-1n. To the best of our knowledge, the synthesis of 1e and 1i was reported for the first time.
Novel Synthesis of Phenol Derivatives by Palladium-Catalyzed Cyclocarbonylation of 2,4-Pentadienyl Acetates
Ishii, Youichi,Gao, Chao,Xu, Wen-Xiang,Iwasaki, Masakazu,Hidai, Masanobu
, p. 6818 - 6825 (2007/10/02)
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 deg 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 41-51percent yield on heating to 160 deg 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, respectively.
