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. Author manuscript; available in PMC: 2019 Aug 20.
Published in final edited form as: J Am Chem Soc. 2019 Jul 30;141(32):12507–12512. doi: 10.1021/jacs.9b06277

Table 1.

Discovery and Optimization of Phosphacatalytic Iterative Condensation/Annulation of Amine and Carboxylic Acid

graphic file with name nihms-1043779-t0002.jpg
Entry R3P=O X+ source Yield (%)a
1 4•[O] DEBM 94 (84)b
2 4•[O] DEMBM 90
3 4•[O] NBS 10
4 4•[O] DECM 0
5 4•[O] CCl4 0
6 5•[O] DEBM 26
7 6•[O] DEBM 46
8 7•[O] DEBM 50
9 8•[O] or 9•[O] DEBM 0
10 none DEBM 0
11 4•[O] none 0
12 4•[O], no PhSiH3 DEBM 0
13 4 DEBM 90
14 [4•Br]Br DEBM 87
a

Yields determined through 1H NMR analysis with the aid of an internal standard. See Supporting Information for full synthetic details and yields of intermediate amide 3a’.

b

Isolated yield on 0.4 mmol scale. DCE = 1,2-dichloroethane; DEBM = diethyl bromomalonate; DEMBM = diethyl (methyl)bromomalonate; NBS = N-bromosuccinimide; DECM = diethyl chloromalonate.