Table 1. Optimization of the Coupling Reaction between Phenylboronic Acid and Diphenylphosphine Oxide.

					product composition (%)a,b
entry	base	solvent	t (h)	conversion (%)a	1a	(EtO)Ph2PO	yield (%) of 1a
1	Cs2CO3	MeCN	2.5c	80	80
2c	Cs2CO3	EtOH	1.5	100	95	5	83
3	Cs2CO3	dioxane	1.5	100	100		79
4	K2CO3	MeCN	2.5d	96	96		78
5	K2CO3	EtOH	1.5	100	97	3	80
6	Et3N	MeCN	1.5	11	11
7	Et3N	EtOH	1.5	22	22

^aOn the basis of relative ³¹P NMR intensities.

^bThe average of two or three parallel experiments.

^cThe coupling was also performed on a larger scale applying 1.0 mmol of PhB(OH)₂ and 1.2 mmol of Ph₂P(O)H. In this case, the yield of 1a was 87%.

^dThe extrapolated reaction time is 3 h.