Table 4.

Spectral characterization of N-ethyl- (4) and N-formyl- (5) (aminomethylene)bisphosphonates and imine-type intermediates 6a and 6b.

Compounds	δP in CDCl3	δP [lit.]	[M + H]+found	[M + H]+requires
4a	19.98	–	388.2020	388.2012
4b	20.63	–	414.2162	414.2169
5a	16.08 and 16.16 (E and Z isomers)	15.69 and 15.98a (E and Z isomers) [43]	388.1659	388.1649
5b	16.00 and 16.06 (E and Z isomers)	–	414.1797	414.1805
6a	–	–	197.1075	197.1073
6b	17.67	–	242.0936	242.0941

^aIn CCl₄.