Synthesis of a novel type of chiral phosphinocarboxylic acids. The phosphine-palladium complexes catalyzed asymmetric allylic alkylation
摘要:
A novel type of chiral cycloalkylphosphines bearing the carboxy group at the beta-position were developed, and used for palladium catalyzed asymmetric alkylation of allylic substrates such as 2-cyclohexenylacetate and 1,3-disubstituted-propenyl acetates (R1CH = CHCH(OAc)R2: R1 = R2 = Ph; R1 = Ph, R2 = (CH2)4OAc; R1 = Ph, R2 = (CH2)6OAc; R1 = Ph, R2 = (CH2)10OAc). Reaction of the propenyl acetates with soft carbon nucleophiles such as triethyl sodiophosphonoacetate and sodiomalonic acid esters in the presence of a palladium catalyst prepared in situ from Pd(OAc)2 and chiral (2-diphenylphosphino)cycloalkanecarboxylic acids (7a,b) gave high yields of alkylation products (PhCH = CHCH(X)Ph: > 77 %ee for X = CH(CO2Et)P(O)(OEt)2 and > 72 %ee for X = CH(CO2Me)2). The alkylation products 15 and 28a-c were converted into optically active alpha-methylene-gamma-lactone and alpha-methylene macrolide derivatives. The high stereoselectivity demonstrated by the chiral phosphinocarboxylic acid-palladium catalyzed allylic alkylation suggested to be caused by an electronic repulsion between the carboxy group on the ligand and the incoming soft carbon nucleophile, which directs the nucleophilic attack on one of the pi-allyl carbons.
Olefins were effectively converted into the corresponding (2-methylthioalkyl)triphenylphosphonium salts by the reaction with dimethyl(methylthio)sulfonium salts in the presence of triphenylphosphine. 2-Triphenylphosphonioalkyldimethylsulfonium salts, synthesized by alkylation of the corresponding methylthiophosphonium salts, react with 1,8-diazabicyclo[5.4.0]undec-7-ene or aq NaOH to afford the corresponding
Copper‐Catalyzed C−P Cross‐Coupling of (Cyclo)alkenyl/Aryl Bromides and Secondary Phosphine Oxides with
<i>in</i>
<i>situ</i>
Halogen Exchange
作者:Paweł Woźnicki、Marek Stankevič
DOI:10.1002/ejoc.202100456
日期:2021.6.25
A protocol for copper-catalyzed halogen exchange/C−P cross-coupling between (cyclo)alkenyl/arylbromides and secondary phosphine oxides has been developed. The addition of sodium iodide increases the yield of the cross-coupling by promoting in situ halogen exchange of organic bromides to the corresponding iodides.
Constant current electrolysis of triphenylphosphine in dichloromethane at a graphite anode in the presence of cycloalkenes gave the corresponding 1-cycloalkenylphosphonium salts in reasonable yields.