Table 2. Catalytic reactivity of K₂MgR₄(PMDETA)₂ with the 18-crown-6 additive towards various structurally diverse alkynols.

Entry a , c	Substrate (5 mol% cat., C6D6)	Yield b
1		99% (14 : 9 : 77)
2		86%
3		89%
4		90%

^aReactions were performed in a Young's cap NMR tube, using 0.6 mmol (1.2 eq.) substrate (3, 5, 7, or 9) and 0.025 mmol (5 mol%) pre-catalyst with 0.1 mmol (20 mol%/0.2 eq.) 1 consumed in converting the pre-catalyst to the ‘active catalyst’ (vide infra).

^bCalculated from ¹H NMR spectroscopic data by integration against an internal standard (10 mol% 1,2,3,4-tetraphenylnaphthalene).

^cA stoichiometric quantity of crown ether co-catalyst used according to the alkali metal [i.e., 10 mol% 18-c-6 for 5 mol% K₂MgR₄(PMDETA)₂].