Triorganozincates as efficient nucleophiles for the diastereoselective addition to N-(tert-butanesulfinyl)imines

Triorganozincates, generated by mixing a Grignard reagent and a dialkylzinc reagent, effectively react with (R)-N-(tert-butanesulfinyl)benzaldimine to give the expected α-branched sulfinamides in good to excellent yields and with diastereomeric ratios of up to 98:2. When the R group of the organomagnesium and the R′ group of the diorganozinc are different, the selective transfer of only one of them to the imine can be achieved by the proper choice of the organometallic reagents. One can take advantage of the slow transfer rate of the methyl group to use it as a non-transferable one. The N-sulfinyl group of the products can be easily removed by acidic treatment, affording the corresponding chiral primary amines without the loss in enantiomeric purity.

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1-Phenylpropan-1-amineC9H13NEe = 90%[α]D20=+11.9 (c 1.1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R)

1-Phenylhexan-1-amineC12H19NEe = 92%[α]D20=+4.0 (c 1.6, EtOH)Source of chirality: asymmetric synthesisAbsolute configuration: (R)

2-Methyl-1-phenylpropan-1-amineC10H15NEe = 88%[α]D20=+6.4 (c 0.6, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R)

1-Phenylprop-2-en-1-amineC9H11NEe = 90%[α]D20=+9.3 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R)