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Antilla reported a transfer hydrogenation of trans‐chalcone derivatives using CPA 6f, employing borane as the hydride source (Scheme 2.70) [156].

Song developed an efficient method for the reduction of 2‐substituted indoles to produce 2‐substituted indolines by the combined use of CPA 6q and catecholborane in the presence of water. The formation of phosphoric acid boron complex 33 was proposed (Scheme 2.71) [157].

Sun accomplished the reduction of 1,1‐diarylethenes by a transfer hydrogenation that used a combination of Hantzsch ester and CPA 6i to afford 1,1‐diarylethanes with 75–99% ee (Scheme 2.72) [158].

Scheme 2.69. Reduction of ketones by the combined use of catecholborane.

Scheme 2.70. Transfer hydrogenation of chalcone derivatives.

Source: Based on [156].

Scheme 2.71. Reduction of indolines.

Source: Based on [157].

Scheme 2.72. Transfer hydrogenation of 1,1‐diarylethenes.

Source: Based on [158].