Diphenyl (2,3-Dihydro-2-thioxo-3-benzoxazolyl)phosphonate: A New, Reactive Condensing Agent for the Synthesis of Amides, Esters, Peptides, and β-Lactams via Condensation
作者:Mitsuru Ueda、Hideharu Mori
DOI:10.1246/bcsj.65.1636
日期:1992.6
Diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (1) prepared from 2-benzoxazolethiol and diphenyl phosphorochloridate was proved to be a very useful condensing agent. A variety of amides, esters, and dipeptides were obtained in excellent yields. Furthermore, this reagent was successfully applied to the synthesis of β-lactams from β-amino acids.
Preparation of β- and γ-lactams from carbamoyl radicals derived from oxime oxalate amides
作者:Eoin M. Scanlan、Alexandra M. Z. Slawin、John C. Walton
DOI:10.1039/b315223e
日期:——
synthetic route to oxime oxalate amides was developed and applied to the preparation of molecules incorporating N-benzyl-N-alkenyl amides linked with acetone oxime or benzaldoxime units. In addition, 2-substituted-thiazolidine-4-carboxylic acid methyl esteramides of oxalyl benzaldoxime were also prepared. It was shown by EPR spectroscopy that the oxalyl benzaldoxime amides dissociated to produce benziminyl
α-Methylene-β-lactams 3 were synthesized from the various 2-bromoallylamine derivatives 2 using a catalytic amount of Pd(OAc)2 or PD(acac)2 and PPh3, under 1–4 atom pressure of CO in good yields. Similarly, α-alkylidene-β-lactams 20 were synthesized from 3-alkyl-2-bromoallylamines 19, which were easily prepared from the olefins 14, in the same manner.
The radicalreaction of benzenethiol with S-4-pentynyl carbamothioates provides a valuable protocol for the tin-free generation of carbamoylradicals, which arise from intramolecular substitution at sulfur by the initial sulfanylvinyl radicals. This procedure can be usefully employed to achieve N-benzylcarbamoyl radical 5-exo and 4-exo cyclizations leading, respectively, to pyrrolidinones and azetidinones
Use of 2,2′-Dibenzothiazolyl Disulfide-Triphenylphosphine and Lawesson’s Reagent in the Cyclization of β-Amino Acids
作者:Seema Kanwar、S. D. Sharma
DOI:10.1246/bcsj.79.1748
日期:2006.11
The disulfide reagents 2,2'-dithiobisbenzothiazole (MBTS) and 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (Lawesson'sReagent, LR) mediate the cyclization of /?-amino acids with remarkable product yields. Compared to other cyclodehydrating agents, these have been found to be superior in terms of their cost, making them industrially viable. The advantageous properties of MBTS