TABLE 1.

One-Pot Diastereoselective Benzopyran Synthesis

	SM	R′M	2π	Cycloadduct	cis/transa	%
1b	3	t-BuMgCl 26			NA	50
2b	4	MeLi 27 + MgBr2			~6:1	27
3b	4	PhMgBr 28			>50:1c	73
4b	4				>50:1c	70
5b	4				>50:1c	86
6b	4	MeMgCl 31			~24:1	66
7d	4	MeMgCl 31			~4:1	55
8e	4	MeLi 27 + MgBr2			NA	57
9e	4	MeLi 27 + MgBr2			NA	58
10d	4				>50:1c	70
11e	4	MeMgCl 31			<1:50c	94
12b	4	MeMgCl 31			>50:1c	76

^aCis/trans ratio determined by ¹H NMR analysis of crude material.

^b2π component used as the solvent for the reaction.

^c>50:1 signifies that no other isomers could be found in the 400-MHz ¹H NMR spectra.

^d5–10 equiv of 2π component used.

^e2–5 equiv of 2π component used.