baɪ tˈɛðɚɹɪŋ ðə kˈɛtoʊn tə ðə hˈaɪdɹaɪd sˈoːɹs ˈoʊnli wˈʌn tɹænsˈɪʃən stˈeɪt ɪz pˈɑːsᵻbəl fˈɪɡjɚ fˈoːɹ lˈiːdɪŋ tə ðɪ ˌeɪsɪmˈɛtɹɪk ɹᵻdˈʌkʃən.
By tethering the ketone to the hydride source only one transition state is possible (Figure 4) leading to the asymmetric reduction.