Towards Benign Synthesis of Indenes from Indanones: Zinc-Mediated Allylation of Ketones in Aqueous Media as a Source of Substituted Indenyl Ligand Precursors
Substituted indenes are valuable ligand precursors for transition-metal complexes. Previously, most of the methods employed for the preparation of alkyl-substituted indenes have involved the use of air-sensitive organometallic lithium or Grignardreagents, often in combination with expensive metal catalysts. The present work evaluates an approach to the synthesis of 2- and 3-allyl-substituted indenes
(±)-1, a recently discovered, valuable, floral-type odorant, has been synthesized by a straightforward procedure (Scheme 1). To determine the properties of the enantiomers of 1, their separation by preparative HPLC and the determination of their absolute configuration by X-ray crystallography were carried out (Figure). Furthermore, the analogues 2–6 were synthesized, either from differently methylated
Unexpected Reactivity of 3-(Phenylethynyl)-1<i>H</i>-indenes towards Nucleophiles: Noncatalytic Addition to Triple Bond with or without Double Bond Migration
作者:P. Ivchenko、I. Nifant’ev、Yu. Luzikov、S. Mkoyan
DOI:10.1055/s-2007-965957
日期:2007.4
When studying the chemical properties of (3-phenylethynyl)-1 H-indenes, a new reaction was discovered, namely, nucleophilic addition to conjugated enynes accompanied in some cases by migration. The reaction takes place under mild conditions and is not catalyzed by transition metal complexes. A putative reaction mechanism via an allene intermediate is discussed.
A catalyst comprising
(i) an asymmetric complex of formula (I)
wherein
M is zirconium or hafnium;
each X is a sigma ligand;
L is a divalent bridge selected from —R′
2
C—, —R′
2
C—CR′
2
—, —R′
2
Si—, —R′
2
Si—SiR′
2
—, —R′
2
Ge—, wherein each R′ is independently a hydrogen atom, C1-C20-alkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl;
R
2
and R
2′
are each independently linear C
1-10
hydrocarbyl;
R
5
and R
5′
are each independently hydrogen or a C1-20 hydrocarbyl group;
R
6
and R
6′
are each independently hydrogen or a C1-20 hydrocarbyl group;
R
7
is hydrogen or a C1-20 hydrocarbyl group or is ZR
3
;
Z is O or S, preferably O;
R
3
is a C1-10 hydrocarbyl group;
Ar is an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R
8
;
Ar′ is an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R
8′
; and
R
8
and R
8′
are each independently is a C1-20 hydrocarbyl group;
with the proviso that at least one of R
6
or R
7
is not H;
and (ii) a cocatalyst comprising a compound of a group 13 metal, e.g. boron.
Stereodivergent Anion Binding Catalysis with Molecular Motors
作者:Ruth Dorel、Ben L. Feringa
DOI:10.1002/anie.201913054
日期:2020.1.7
A photoresponsive chiral catalyst based on an oligotriazole-functionalized unidirectional molecular motor has been developed for stereodivergent anion binding catalysis. The motor function controls the helical chirality of supramolecular assemblies with chloride anions, which by means of chiralitytransfer enables the enantioselective addition of a silyl ketene acetal nucleophile to oxocarbenium cations