Further optimizations were carried out with reagent 2c (Table ). When the number of equiv. of NaH was lowered to 1.5, the yield increased substantially (59%, Table , entry 3 vs entries 1-2). Lowering the amount of NaH further, or lowering the amount of amine 3 did not have a significant effect on the yield (Table ). On the other hand, with 1.5 equiv. of 2c, a yield of 68% was obtained (Table , entry 6). Importantly, when the triisopropylsilyl group (TIPS, 1a-TIPS) was replaced by a tert-butyldimethylsilyl group (1a-TBS, Table , entry 7), product 5a was obtained in 77% yield. The less hindered trimethylsilyl group (1a-TMS, Table , entry 8) gave a lower yield. We also tested toluene, THF, 2-methyltetrahydrofuran, and acetone as reaction solvents, but the desired product was not observed (Table , entry 9). 9 TBS 1.5 2 1.5 -