Table 2.

Investigation of the reaction between compound 12, phosphonoacetates 8 and BTMS.^a

entry	R1	R2	TEA	ratio 12:21
1	t-Bu	Et	6	0.18:0.82
2	t-Bu	Et	3	0.58:0.42
3	t-Bu	Et	–	1:0
4	Et	iPr	10	1:0

^aReactions carried out for 24 h at 35 °C in the presence of the appropriate phosphonoacetate (see Scheme 5) using distilled BTMS.