Electron transfer photoinduced cleavage of acetals. A mild preparation of alkyl radicals
摘要:
Electron transfer from 2-alkyl- and 2,2-dialkyldioxolanes as well as from open-chain ketals to singlet excited benzene-1,2,4,5-tetracarbonitrile (TCNB) is followed by fragmentation of the donors radical cation to yield alkyl radicals and dialkoxy carbocations. The first species are trapped by TCNB to yield alkylbenzenetricarbonitriles (substitution of a second cyano group can be obtained sequentially) and in a minor path are reduced to alkanes, while the latter ones react with nucleophiles to give ortho acid derivatives. In view of the results of radical clock experiments, it is assumed that part of the process is a concerted (radical cation cleavage-addition to the aromatic) reaction, while another part involves the free-radical cation. On the other hand, intersystem crossing from the singlet radical ion pair to the triplet manifold causes cleavage of the acetal to the corresponding carbonyl derivative. This reaction offers a mild method for the preparation of alkyl radicals via C-C bond cleavage.
Total Synthesis of the Polyether Antibiotic Lonomycin A (Emericid)
作者:David A. Evans、Andrew M. Ratz、Bret E. Huff、George S. Sheppard
DOI:10.1021/ja00117a014
日期:1995.3
The first asymmetric synthesis of the polyetherantibiotic lonomycin has been achieved. The skeleton is assembled through the synthesis and union of two subunits comprising the CI-CII and C12-C3o portions of the structure. These fragments were constructed utilizing auxiliary-based asymmetric aldol and acylation reactions to control the absolute stereochemical relationships in the structure. The majority
Pyranone compounds useful to treat retroviral infections
申请人:Pharmacia & Upjohn Company
公开号:US05852195A1
公开(公告)日:1998-12-22
The present invention relates to compounds of formulae (I) and (II) which are pyran-2-ones, 5,6-dihydro-pyran-2-ones, 4-hydroxy-benzopyran-2-ones, 4-hydroxy-cycloalkyl\x9bb!pyran-2-ones, and derivatives thereof, useful for inhibiting a retrovirus in a mammalian cell infected with said retrovirus, wherein R.sub.10 and R.sub.20 taken together are formulae (III) and (IV). ##STR1##
Synthese electrochimique de methoxy-2 dioxa-1,4 cyclanes par oxydation anodique de cetals cycliques de β-ceto-carboxylates
作者:Daniel Lelandais、Cathy Bacquet、Jacques Einhorn
DOI:10.1016/s0040-4020(01)98845-3
日期:1981.1
Anodicoxidation of β-oxocarboxylate cyclic acetals in anhydrous methanol gives 2-methoxy-1,4-diox-acycloalkanes in 40–60% yields. The mechanism is discussed.
Homogeneous catalysis. Use of the [TiCp2(CF3SO3)2] catalyst for the sakurai reaction of allylic silanes with orthoesters, acetals, ketals and carbonyl compounds.
作者:T. Keith Hollis、N.P. Robinson、John Whelan、B. Bosnich
DOI:10.1016/s0040-4039(00)79336-1
日期:1993.7
The effectiveness of the [TiCp2(CF3SO3)2] catalyst for the Sakurai reaction has been explored for a variety of allylic silanes reacting with orthoesters, acetals, ketals, aldehydes and ketones.
对于与原酸酯,缩醛,缩酮,醛和酮反应的各种烯丙基硅烷,已经探索了[TiCp 2(CF 3 SO 3)2 ]催化剂在樱井反应中的有效性。
The Reactions of Electron-Rich Heterocycles with Derivatives of Orthocarboxylic Acids; VIII. Proton Acid-Catalyzed Acylation of Indoles by 2-Alkoxy-1,3-dioxolanes
作者:Eyüp Akgün、Mustafa Tunali、Ulf Pindur
DOI:10.1002/ardp.19873200504
日期:——
In acid‐catalyzed reactions with 3‐unsubstituted indoles 1, 2‐alkoxy‐1,3‐dioxolanes 2a‐c behave as acyl equivalents. Depending on the substitution patterns of the reaction partners, the 1,3‐dioxolanium ions 3a‐c, generated in situ from the cyclic ortho esters by the action of sulfosalicylic acid, react to form tris‐(3‐indolyl)alkanes 6 and 9, bis‐(3‐indolyl)ethenes 7, or 3‐benzoylindoles 8. Analogous