Table 1.

Optimizations To Synthesize the Pivotal α-Chloroglycin Ester 6a

entry	solvent, tempa	activator	time (h)	conversion (%)b
1	CHCl3, rt		12	5a (62)c
2	CHCl3, rt	AcCl	18	5a (76); 6a (4)
3	CH3CO2Et, rt		12	5a (82)c
4	CH3CO2Et, rt	AcCl	18	5a (59); 6a (19)
5	CH3CO2Et, 60 °C	AcCl	9	6a (100)
6	CHCl3, 60 °C	AcCl	12	6a (100)
7	THF, 60 °C	AcCl	12	5a (61); 6a (25)d
8	toluene, 60 °C	AcCl	12	5a (44); 6a (56)
9	CH3CN, 60 °C	AcCl	24	6a (100)

^aReactions were performed with 2a (1.0 mmol), 3a (1.3 mmol), acetyl chloride (2.5 mmol), and acetic acid (10 mol %).

^bConversions were reported due to the innate instability of chloroaminal 6a, using a quantitative 1H NMR technique²¹ with mesitylene as an internal standard.

^cIsolated yields of pure hemiaminal 5a were 60% and 81% for entries 1 and 3, respectively.

^dDecomposition and possible polymerization were observed.