Table 3.

Reaction Generality.

For comparison, yields and diastereoselectivities for selected reactions conducted for 18 h without additive 23 are given in square brackets. Each diastereomeric ratio (dr) was determined on the crude mixture after passing through a short plug of silica gel.

^aYield was determined by ¹H NMR spectroscopy with 1,1,2,2-tetrachloroethane (1.0 equiv) as an internal standard.

^b91:9 dr at C(1) after isolation.

^c24% of the free alcohol syn-dichloride was also isolated, and tentatively assigned cyclized products were also observed in the crude product mixture.

^d21% of the free alcohol syn-dichloride was also isolated.

^eThe dr corresponds to the sum of the dichlorides.

^fAdditive 23 was omitted.

^g97:3 dr after isolation.