146514-06-9Relevant academic research and scientific papers
Rare-Earth-Metal-Complex-Catalyzed Hydroalkoxylation and Tandem Hydroalkoxylation/Cyclohydroamination of Isocyanates: Synthesis of Carbamates and Oxazolidinones
Zhu, Xiancui,Qi, Yawen,Yang, Yuanqing,Guo, Dianjun,Huang, Zeming,Zhang, Lijun,Wei, Yun,Zhou, Shuangliu,Wang, Shaowu
, p. 3202 - 3211 (2022/02/23)
Novel N,N,N-tridentate β-diketiminato rare-earth-metal dialkyl complexes LRE(CH2SiMe3)2 [RE = Y (1a), Gd (1b), Yb (1c), Lu (1d); L = MeC(NDipp)CHC(Me)N(CH2)2NC4H8, where Dipp = 2,6-iPr2C6H3] have been conveniently synthesized by one step from reactions of the rare-earth-metal trialkyl complexes RE(CH2SiMe3)3(THF)2 (THF = tetrahydrofuran) with a pyrrolidine-functionalized β-diketiminate HL, and their catalytic behaviors toward hydroalkoxylation and tandem hydroalkoxylation/cyclohydroamination of isocyanates have been described. These rare-earth-metal catalysts exhibited high efficiency in the hydroalkoxylation of isocyanates, providing a variety of N-alkyl and N-aryl carbamate derivatives under mild reaction conditions with a rather low catalyst loading (0.04 mol %). More significantly, they can promote a tandem hydroalkoxylation/cyclohydroamination reaction between terminal and internal propargylic alcohols with substituted arylisocyanates, leading to the efficient synthesis of methylene and (Z)-selective arylidene oxazolidinones in good-to-high yields via consecutive C-O and C-N bond formation. The stoichiometric reaction of 1a with p-tolylisocyanate generated an unusual dinuclear yttrium complex, {[η2-(4-MePhNCO)(CH2SiMe3)]Y[μ-η2:η1:η1-(4-MePhNCO)CC(Me)(NDipp)C(Me)N(CH2)2NC4H8]}2 (7a), with two different amidate units, which underwent an sp2 C-H bond activation of the β-diketiminato backbone, followed by the insertion of isocyanate.
On the stereochemical course of palladium-catalyzed cross-coupling of allylic silanolate salts with aromatic bromides
Denmark, Scott E.,Werner, Nathan S.
supporting information; experimental part, p. 3612 - 3620 (2010/05/01)
The stereochemical course of palladium-catalyzed cross-coupling reactions of an enantioenriched, a-substituted, allylic silanolate salt with aromatic bromides has been investigated. The allylic silanolate salt was prepared in high geometrical (Z/E, 94:6) and high enantiomeric (94:6 er) purity by a coppercatalyzed SN2′ reaction of a resolved allylic carbamate. Eight different aromatic bromides underwent crosscoupling with excellent constitutional site-selectivity and excellent stereospecificity. Stereochemical correlation established that the transmetalation event proceeds through a syn SE′ mechanism which is interpreted in terms of an intramolecular delivery of the arylpalladium electrophile through a key intermediate that contains a discrete Si-O-Pd linkage.
Base catalyzed cyclization of N-aryl and N-alkyl-O-propargyl carbamates to 4-alkylidene-2-oxazolidinones
Ramesh, Ramapanicker,Chandrasekaran, Yogesh,Megha, Rajendran,Chandrasekaran, Srinivasan
, p. 9153 - 9162 (2008/02/10)
The base catalyzed cyclization of N-aryl and N-alkyl-O-propargyl carbamates is studied in detail. The effect of various bases and solvents on the efficacy of this cyclization reaction is analyzed and a new base-solvent system (LiOH in DMF) for effective cyclization of these carbamates is reported. A number of differentially substituted O-propargyl carbamates were cyclized to the corresponding 2-oxazolidinones under these conditions. The reaction conditions reported here are mild and no side reactions were observed in any of the substrates studied. A propargyl carbonate group was unaffected during the course of the cyclization of the O-propargyl carbamate group. The propargyl carbamates were prepared from the corresponding alkyl or aryl amines and the corresponding propargyl chloroformate, resulting in oxazolidinones diversely substituted at the nitrogen atom. N-Aryl-O-propargyl carbamates cyclized readily to the corresponding oxazolidinones with LiOH in DMF, whereas N-alkyl-O-propargyl carbamates reacted slowly under the same conditions. O-Propargyl carbamates substituted at the 1-position tend to cyclize faster whereas those substituted at 3-position cyclize considerably slower than the unsubstituted carbamates.
