Novel method for transforming aldehydes and acetals into 1,3-dithianes has been achieved with the aid of organotin thioalkoxides and organotin triflates. Under these reaction conditions, various acid-sensitive groups are tolerated. Differentiation between aromatic or aliphatic aldehydes and acetals has been realized.
Differentiation between carbonyls and acetals in 1,3-dithiane and 1,3-dithiolane synthesis catalyzed by organotin triflates
作者:Tsuneo Sato、Junzo Otera、Hitosi Nozaki
DOI:10.1021/jo00070a038
日期:1993.8
Carbonyls and acetals are converted to 1,3-dithianes and -dithiolanes upon treatment with 2-stanna-1,3-dithianes and -dithiolanes under catalysis by organotin triflates. In these competition reactions, various types of carbonyls and acetals are differentiated. Aldehydes react preferentially over ketones, but the preference is completely reversed in the competition reactions between the corresponding acetals and ketals. The reactivity of aliphatic aldehydes is greater than that of the acetals of aliphatic aldehydes and ketones. Conversely, an aromatic acetal is more reactive than its parent aldehyde. In the competition between aromatic and aliphatic aldehydes, the reaction of the latter predominates. However, aromatic acetals react preferentially over aliphatic acetals. Ketones of different types are also differentiated. No such discrimination can be achieved by conventional methods. Organotin triflates are capable of detecting subtle differences in the reactivity of carbonyls and acetals. Such unique differentiation can be explained in terms of the dependence of the reaction path on the substrate: the reactions of carbonyls are initiated by coordination to tin, whereas the reactions of acetals proceed via oxocarbenium ion intermediates.
Design and synthesis of a selective EP4-Receptor agonist. Part 1: discovery of 3,7-DithiaPGE1 derivatives and identification of Their ω chains
Improvement of EP4-receptor selectivity and the agonist activity by introduction of heteroatoms into the a chain of PGE(1) was investigated. Among the compounds tested, 3,7-dithiaPGE(1) 4a exhibited good EP4-receptor selectivity and agonist activity. Further modification of the omega chain of 3,7-dithiaPGE(1) was performed to improve EP4-receptor selectivity and agonist activity. Of the compounds produced, 16-phenyl-omega-tetranor-3.7-dithiaPGE(1) 4p possessing moderate EP4-receptor selectivity and agonist activity. was identified as a new chemical lead for further optimization by modification of the aromatic moiety. (C) 2002 Elsevier Science Ltd. All rights reserved.
SATO, TSUNEO;YOSHIDA, ENJI, KOBAYASHI TAKAMICHI;OTERA, JUNZO;NOZAKI, HITO+, TETRAHEDRON EDRON LETT., 29,(1988) N 32, C. 3971-3974