Tin Mediated Addition of Secondary and Tertiary Radicals

The first test of the chiral N acylhydrazones was in tin mediated radical addition [24]. 

Addition of isopropyl iodide to propionaldehyde hydrazone 8a was chosen for initial 

A variety of aldehyde hydrazones were screened [24b]. Branching at a saturated a carbon was detrimental in the tin mediated radical additions, but an aromatic benzaldehyde hydrazone 12 offered some success, with yields ranging from 30 to 83% (Table 2.3, entries 5 8). With the exception of 8a, which decomposed under the reaction conditions, the reactions were quite dean. Even in the examples with lower yields, the mass balance after recovery of the hydrazone precursor was generally 80 90%, demonstrating the excellent chemoselectivity of the reactions of radicals with N acylhydrazones. We were delighted to find that the radical additions had occurred with excellent stereocontrol in all secondary and tertiary radical additions to hydrazones 8 and 12 (Table 2.3), with diastereomer ratios ranging from 93 7 to 99 1 [24]. 

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