Chiral phosphorus compounds are of great important in the fields of pharmaceutical chemistry1, materials2 and typically used as versatile ligands3 or oganocatalysts4 in asymmetric catalysis. Generally, transition-metal1a,5 or inorganic base6-promoted asymmetric P-C bond formation constitutes one of prominent strategy for the preparation of chiral phosphorus compounds possessing chiral centers at phosphorus and/or carbon atmos. In the recent years, organocatalytic asymmetric P-C bond formation from P-H species received more and more attention.7 This strategy provided a variety of efficient and green ways for the preparation of serious versatile chiral phosphorus compounds. To date, these studies were committed to processes that control a single …show more content…
b Isolated yields. c Determined by 31P NMR of the crude reaction mixture. d Na2CO3 (1.5 equivalent ) as additive. e 4Å MS (2.0 equivalent) was added. f The reaction conducted at 10 oC The scope of the asymmetric P-C bond formation reaction was then examined under the optimized conditions identified above. As is shown in Table 2, in generally, the desired products can be successfully obtained in high yields, irrespective the electronic properties and position of the aryl-substituents on allylic carbonates (entries 1-3, 5-12). The ketone derivative 2 was also a suitable partner for this reaction, albeit gave the desired 4d with a lower yield (entry 4). In all the tested reaction, all the configuration of phosphorus was stable and maintained (RP/SP > 99/1). The diaselectivity was generated in the adjacent carbon center, and proved sensitive to the variation of the substitution on the phenyl groups. Electro-with drawing group, to some extent, disfavor the diaselectivity (entries 6, 11). In addition, this transformation can performed in gram scale with comparable result associate with the yield and selectivity (entry 8). MBH carbonates with thiophen-2-yl substituent could also afford the corresponding product in high yield with good selectivity (entry 14). However, aliphatic substituents in MBH …show more content…
b Isolated yields. c Determined by 31P NMR of the crude reaction mixture. d 2.5 equivalent of 2 was used. e The result at 10 oC. f The reaction performed in gram scale (2.5 mmol) and 4g was isolated in 1.08g. Figure 2. X-Ray crystal structure of 4g. We further examined the scope of the asymmetric P-C bond formation by using (RP)-menthylphosphine oxide 1b as the partner and the results are listed in Table 3. Under the same conditions, (RP)- menthylphosphine oxide 1b could afford the desired product with higher yield and selectivity compared with the corresponding (RP)-O-(-)-menthyl H-phenylphosphinate 1a. Both electro-donating and electro-withdrawing substituents on the aryl group of 2 were well tolerated. Moreover, ketone derivative 2 delivered a higher yield (79%) of corresponding product 5c. Table 3. Asymmetric P-C bond formation between (RP)-menthylphenylphosphine oxide 1b and allylic carbonates a entry R1 EWG 5, yield (%)b d.r.C c 1 4-BrC6H4 CO2Et 5a,98