Table 2.

Screening of different chiral phosphoric acid (CPA) catalysts.

Entry	Chiral Phosphoric Acid (CPA)	Conv. [%][a]	ee [%][b]
1	(S)‐11	>99	<1
2	(R)‐12	>99	17[c]
3	(S)‐13	>99	27
4	(S)‐15	>99	33[d]
5	(R)‐14	>99	44[c]
6	(S)‐9	>99	70

Reaction conditions: ketone (0.1 mmol), zinc (5 eq.), NH₄Cl (8 eq.), CPA (10 mol‐%), 7 b (1.5 eq.) in toluene (1 mL) and cyclohexane (1 mL); spontaneous lactonization to product 10 b was observed for all entries.

^[a] Conversions were determined via HPLC‐UV (215 nm).

^[b] The enantiomeric excess was determined on a chiral stationary phase via normal phase HPLC‐UV (215 nm).

^[c] The opposite enantiomer was observed [note: the (R)‐CPA has been used in case of these entries].

^[d] The opposite enantiomer was observed [note: reagent 7d was used in case of this entry].