Experimental and calculated second-order rate constants k₂ for the reactions of the Michael acceptors 1–5 with the reference nucleophiles 6–7 in DMSO at 20 °C.

Electrophiles	Nucleophiles	k exp 2 (M−1 s−1)	k eqn (1) 2 (M−1 s−1)	k exp 2/keqn (1)2
1a, E = −20.6a	6a	1.51 ± 0.05	6.1 × 10−1	2.5
	7	1.06 ± 0.05	2.1	0.51
	6c	(1.62 ± 0.01) × 102	1.8 × 102	0.89
1b, E = −22.1a	6a	(3.69 ± 0.19) × 10−2	7.7 × 10−2	0.48
	7	1.05 ± 0.02	2.0 × 10−1	5.3
	6c	7.83 ± 0.85	5.1 × 101	0.15
1c (E = −28.9)a,b	6c	(1.55 ± 0.18) × 10−1	—	—
2a, E = −22.1a	6a	(7.60 ± 0.36) × 10−2	7.7 × 10−2	0.99
	7	(5.16 ± 0.12) × 10−1	2.0 × 10−1	2.6
	6c	(1.07 ± 0.01) × 101	5.1 × 101	0.21
2b (E = −27.5)a,b	6c	(5.00 ± 0.49) × 10−1	—	—
2c (E = −29.6)a,b	6c	(8.70 ± 1.31) × 10−2	—	—
3, E = −22.0a	6a	(8.13 ± 0.49) × 10−2	8.8 × 10−2	0.92
	7	(5.31 ± 0.17) × 10−1	2.3 × 10−1	2.3
	6c	(1.19 ± 0.05) × 101	5.5 × 101	0.22
4a, E = −20.7a	6a	(4.14 ± 0.10) × 10−1	5.3 × 10−1	0.78
	7	2.89 ± 0.16	1.8	1.6
	6c	(8.09 ± 0.02) × 101	1.7 × 102	0.48
4b, E = −19.4a	6a	5.47 ± 0.27	3.2	1.7
	7	8.39 ± 0.38	1.4 × 101	0.61
	6c	(6.06 ± 0.12) × 102	5.1 × 102	1.2
5a, E = −21.8a	6a	(9.68 ± 0.27) × 10−2	1.2 × 10−1	0.84
	7	(4.12 ± 0.08) × 10−1	3.2 × 10−1	1.3
5b, E = −19.5a	6a	6.62 ± 0.23	2.8	2.4
	7	5.10 ± 0.04	1.2 × 101	0.44
	6c	(6.01 ± 0.14) × 102	4.7 × 102	1.3

^aThis work.

^bElectrophilicity E estimated on the basis of only one rate constant k^exp₂.