ligands in titanium tetraisopropoxide promoted enantioselectiveaddition of phenylacetylene to benzaldehyde and selected aromatic and aliphatic aldehydes. The N-3,5-bis(trifluoromethyl)benzenesulfonamido-d-glucosamine derivative was chosen as the most efficient ligand for this addition. The reaction is highlyenantioselective for several aromatic aldehydes and enantiomeric excesses up to 92% were obtained
Enantiospecific synthesis of 1,3-disubstituted allenes by palladium-catalyzed coupling of propargylic compounds with arylboronic acids
作者:Masahiro Yoshida、Tatsuro Okada、Kozo Shishido
DOI:10.1016/j.tet.2007.05.035
日期:2007.7
An enantiospecific coupling of propargylic esters and carbonates with arylboronicacids has been developed using a palladium catalyst. Optically active 1,3-disubstituted allenes were synthesized with high enantiomeric excesses by carrying out the reactions under basic aqueous conditions.
Utilization of whole cell mediated deracemization in a chemoenzymatic synthesis of enantiomerically enriched polycyclic chromeno[4,3-b] pyrrolidines
作者:Thangavelu Saravanan、Sushital Jana、Anju Chadha
DOI:10.1039/c4ob00615a
日期:——
Various aryl and alkyl substituted optically pure propargyl alcohols were obtained with excellent ee (up to >99%) and isolated yields (up to 87%) by deracemization using whole cells of Candida parapsilosis ATCC 7330. The whole cells show substrate specificity towards alkyl substituted propargyl alcohols and a switch in the enantioselectivity has been observed from ‘R’ to ‘S’ upon increasing the chain
通过使用副念珠菌ATCC 7330的全细胞进行消旋,获得了各种具有芳烃和烷基取代基的光学纯炔丙醇,具有优异的ee(最高> 99%)和分离的收率(最高87%)。整个细胞显示出对烷基取代的底物特异性随着链长的增加,已观察到炔丙醇和对映选择性的变化,从“ R ”变为“ S ”。对映体纯(R)-4-(3-羟基丁-1-炔基)苄腈,(R)-4-(联苯-4-基)丁-3-炔-2-醇,(S)- 3-羟基-5-苯基戊-4-酸乙酯和(S使用该策略获得了)-4-苯基丁-3-炔-1,2-二醇。如此获得的光学纯的炔丙醇用作手性起始原料,成功合成了对映体富集的多取代的吡咯烷和吡咯衍生物,成功地证明了化学酶促路线。
Enantioselective Alkynylation of Aromatic Aldehydes Catalyzed by a Sterically Highly Demanding Chiral-at-Rhodium Lewis Acid
The enantioselective catalytic alkynylation of aromatic aldehydes is reported using a sterically highly hindered bis-cyclometalated rhodium-based Lewis acid catalyst featuring the octahedral metal as the only stereogenic center. Yields of 58–98% with 79–98% enantiomeric excess were achieved using 1–2 mol % of catalyst. This work complements previous work from our laboratory on the enantioselective alkynylation
naphthyl 1-propargyl ethers through para-Claisen rearrangement was described, and chirality transfer was observed. Moreover, the enantioselective dearomatization of C4-substituted substrates was realized by using a chiral N,N′-dioxide/CoII complex catalyst. The DFT calculations and experimental results support the ortho-Claisen rearrangement/Cope rearrangement sequence process.