Table 5.

Synthesis of (dialkylaminomethylene)bisphosphonates 8a–g.

Entry	Y1	Y2	Yield (%)a
1	Et	Et	86 (8a)
2	Bu	Bu	68 (8b)
3	Bu	Me	79 (8c)
4	c-Hex	Me	72 (8d)
5	Bn	Me	70 (8e)b
6c	Ph	Me	65 (8f)
7	-(CH2)2-O-(CH2)2-		81 (8g)d

^aIsolated yield. ^bIt was synthesized in a yield of 61% [10]. ^c4.5 equivalents of diethyl phosphonate was used.^dIt was synthesized in a yield of 46% [4].