An efficient and chemoselective method for preparation of acetals and dithioacetals of aldehydes and their deprotection under catalysis of InF3 is described.
描述了一种有效的和化学选择性的方法,用于制备醛的缩醛和二硫缩醛并在InF 3催化下将它们脱保护。
Carbon Tetrabromide/Sodium Triphenylphosphine-m-sulfonate (TPPMS) as an Efficient and Easily Recoverable Catalyst for Acetalization and Tetrahydropyranylation Reactions
作者:Congde Huo、Tak Hang Chan
DOI:10.1002/adsc.200900102
日期:——
A solid complex, conveniently prepared from carbontetrabromide and sodiumtriphenylphosphine-m-sulfonate (TPPMS), can be used as an easilyrecoverablecatalyst for the selective acetalization of aldehydes and tetrahydropyranylation of alcohols. The catalyst can be recovered by simple precipitation with ether and can be reused at least 7 times without loss of catalytic activity.
Supported Tetrahedral Oxo-Sn Catalyst: Single Site, Two Modes of Catalysis
作者:Evgeny V. Beletskiy、Xianliang Hou、Zhongliang Shen、James R. Gallagher、Jeffrey T. Miller、Yuyang Wu、Tiehu Li、Mayfair C. Kung、Harold H. Kung
DOI:10.1021/jacs.5b13436
日期:2016.4.6
active in hydride transfer reactions as a typical solidLewisacid. However, the Sn centers can also create Brønsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the neighboring Sn-O-Si bond. The resulting acidic silanol is active in epoxide ring opening and acetalization reactions.
接枝在二氧化硅上的 (POSS)-Sn-(POSS) 复合物在臭氧中温和煅烧产生了一种多相催化剂,该催化剂主要保留了其均相前体的四面体配位,如使用 EXAFS、NMR、UV-vis 和 DRIFT 的光谱表征所证明的. Sn 中心是可接近的且均匀的,并且可以通过化学计量的吡啶中毒进行量化。这种 Sn 催化剂在氢化物转移反应中作为典型的固体路易斯酸具有活性。然而,Sn 中心也可以通过将醇强结合为醇盐并将羟基 H 转移到相邻的 Sn-O-Si 键来与醇产生布朗斯台德酸性。所得酸性硅烷醇在环氧化物开环和缩醛化反应中具有活性。
ZWITTERIONIC PHOSPHONIUM SALTS
申请人:Chan Tak-Hang
公开号:US20110263879A1
公开(公告)日:2011-10-27
A zwitterionic phosphonium salt of Formula I: wherein n is 0 or 1; R is H or SO
3
; R′ is selected from the group consisting of C
1
-C
10
alkyl, C
2
-C
10
alkenyl, C
2
-C
10
alkynyl, C
3
-C
10
cycloalkyl, phenyl, substituted phenyl, benzyl and C
1
-C
10
alkoxy-carbonyl; R′ is CX
3
when n is O; and X is selected from the group consisting of F, Cl, Br and I. The zwitterionic phosphonium salts are useful reagents for the preparation of alkenes and acetals from the corresponding aldehyde.
Enantioselective synthesis of crotyl geminal bis(silane) and its usage for asymmetric Sakurai allylation of acetals
作者:Yang Chu、Qiang Pu、Zhixing Tang、Lu Gao、Zhenlei Song
DOI:10.1016/j.tet.2017.05.011
日期:2017.6
Enantioselective synthesis of crotyl geminal bis(silane) 4 has been developed by an asymmetric [1, 5]-hydride shift of allylic hydrazine. SnCl4-promoted Sakurai allylation of (R)-4 with acetals leads to chemoselective desilylation of SiMe3, generating E-syn-(S, R)-5 in good yields with high E/Z-, diastereo- and enantioselectivity.