Bicyclic molecule

About: Bicyclic molecule is a research topic. Over the lifetime, 29587 publications have been published within this topic receiving 451252 citations. The topic is also known as: bicyclic molecule.

Enantioselective synthesis of tertiary .alpha.-hydroxy carbonyl compounds using [(8,8-dichlorocamphoryl)sulfonyl]oxaziridine

Abstract: Very high stereoinduction, generally 90-95% ee, is observed for the asymmetric oxidation of 2-substituted-1-tetralone enolates to 2-hydroxy-2-substituted-1-tetralones by chiral nonracemic oxaziridine. Not only are these α-hydroxy carbonyl compounds difficult to prepare enantiomerically pure via other methods, but they are also models for several biologically active compounds

Synthesis of the ABC ring system of brevetoxin B

Abstract: La synthese du squelette pyranno [2,3-b] pyranne de la brevetoxine B est effectuee; le compose obtenu comporte un phosphonium quaternaire

Homo- und Hetero-Metall-Amide des Tris(tert-butylamino)methylsilans – Polycyclen und Cluster mit Li, Na, Mg, Al und Tl

Abstract: Homo and Hetero Metal Amides of Tris(tert-butylamino)methylsilane – Polycycles and Clusters with Li, Na, Mg, Al and Tl The hydrogen atoms attached to nitrogen in tris(tert-butyl-amino)methylsilane (1) can be substituted by metallic main-group elements in a quite general way. If 1 is treated with trimethylaluminium apart from the monosubstituted product MeSi(tBuNH)2(tBuNAlMe2) (2) the trisamide MeSi(tBuNAlMe2)3 (3) is obtained. In similar ways complete substitution of the amino hydrogen atoms in 1 yields the compounds MeSi[tBuNMgN(SiMe3)2]3 (6), [MeSi(tBuNLi)3]2 (10), and [MeSi(tBuNTl)3]2 (11), the later two being dimeric. If methyl-magnesium iodide is allowed to react with 1 the intermediate MeSi(tBuNMgI)3 (4) in some instances can be isolated as the THF adduct or may react with a further equivalent of the Grignard compound to generate the complex [MgI-(THF)5]+ [MeSi(tBuNMgI)3CH3 · THF]– (5). The aluminium compound 2 has been used to access to heterometallic amides combining aluminium and sodium as in MeSi(tBuNAlMe2)(tBuNNa)(tBuNH) (7) or magnesium and aluminium as in the dimeric compounds [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgI)]2 (8) and [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgMe)]2 (9). X-ray structure analyses reveal 3 (tricyclic SiN3Al3 skeleton with Al – N distances from 2.014 to 2.025 A), 6 (tricyclic Si-N3Mg3 skeleton), and 7 [bicyclic SiN3AlNa skeleton with Na – N distances of 2.47(1) and 2.52(1) A] to be monomeric even in the solid state. The compounds 8 and 9 (both pentacyclic with spiro magnesium atoms) form centrosymmetric dimers by Mg – I – Mg and Mg – (CH3) – Mg bridges, respectively. The dimers 10 and 11 are completely different in terms of chemical bonding: while in the lithium compound 10 a centrosymmetric polycycle is formed by principly ionic interactions of the lithium atoms with corresponding nitrogen atoms, the centrosymmetric dimer in 11 is held together by Tl – Tl bonds. The X-ray structure analysis of 5 reveals the anion containing a Mg-coordinated CH3–.

Interception of a Rautenstrauch Intermediate by Alkynes for [5+2] Cycloaddition: Rhodium-Catalyzed Cycloisomerization of 3-Acyloxy-4-ene-1,9-diynes to Bicyclo[5.3.0]decatrienes

Abstract: In 1984, Rautenstrauch reported that the 3-acyloxy-1,4-enyne 1 could undergo cyclization to form cyclopentadiene 2 and cyclopentenone 3 in the presence of a palladium catalyst through 1,2-acyloxy migration (Scheme 1).[1] The vinyl metal complex 4, metal carbene 5, and metallacyclohexadiene 6 were proposed as intermediates in this transformation.[1,2] The scope of this rearrangement reaction has been expanded significantly by the use of π-acidic metals,[3] such as gold- and platinum-based catalysts, for the synthesis of functionalized five-membered rings.[4] The 1,2-acyloxy migration of propargyl esters has also been employed in other synthetically useful transformations catalyzed by gold,[5,6] platinum,[6,7] ruthenium,[8,9] copper,[6] and more recently rhodium.[10]