Syntheses of Substituted Indan-1-onesand Indenes

The syntheses of three novel substituted indanones namely 2,7 dimethylindan 1 one, 2 methyl 4,7 diethylindan 1 one and 2,4 dimethyl 7 methoxyindan 1 one are described. These indanones were prepared by different routes involving intramolecular ring closure of aryl substituted compounds by Friedel Crafts reaction. The t butyl was used as the positional protective group in the selective preparation of 2,7 dimethylindan 1 one. The corresponding indenes were prepared by reduction and dehydration reactions from these indanones.

Metal-Free Arylsulfonyl Radical Triggered Cascade Cyclization of Phenyl-Linked 1,6-Enynes:Synthesis of 2,3-Dihydro-1H-indenes and 10a,11-Dihydro-10H-benzo[b]fluorines

Aryl sulfonyl radical triggered cascade cyclization of phenyl-linked 1,6-enynes for the synthesis of biologically important indenes containing alkenyl C—X bonds and 10a,11-dihydro-10H-benzo[b]fluorines is presented.In these radical cascade processes,three new chemical bonds,including C—S,C—C,and C—X bonds,and three C—C bonds are formed in one step.The method is attractive and valuable due to its metal-free,mild reaction conditions,broad substrate scope and good functional group tolerance.

Synthesis and Acid-Catalyzed Cyclization of 2-Alkenylstilbenes： a New Approach to the Substituted Indenes

A base-catalyzed ring-opening of 1-benzylisochromans 1 firstly produced 2-alkenylstilbenes 2, which then underwent a mild acid-catalyzed intramolecular cyclization to furnish 1,2-disubstituted indenes 3 in high yields. Subsequently, a base-catalyzed isomerization of the 1,2-disubstituted indenes 3 afforded the more stable 2,3-disubstituted indenes 4 in almost quantitative yields.

Gold-catalyzed ketene dual functionalization and mechanistic insights:divergent synthesis of indenes and benzo[d]oxepines

An unprecedented gold-catalyzed ketene C=O/C=C bifunctionalization method has been developed.Mechanistic studies and density function theory(DFT)calculations indicate that the reaction is initiated by gold-catalyzed Wolff rearrangement of diazoketone to form the ketene intermediate,followed by intermolecular nucleophilic addition and terminated with two divergent cyclization processes via enol intermediates.In the case with alcohols as the nucleophiles,the reaction goes through a C-5-endodig carbocyclization to give the indene products;whereas,O-7-endo-dig cyclization occurs dominantly when indoles/pyrroles are used as the nucleophiles,delivering the 7-membered benzo[d]oxepines.In comparison with the well-documented cycloaddition and nucleophilic addition reactions,this cascade reaction features a novel reaction pattern for the ketene dual functionalization through addition with nucleophile and electrophile in sequence.

Synthesis and Crystal Structure of 1-(4-Chlorophenyl)-2-cyano-3-amino-3a-hydroxy- 3a,3b,6,7-tetrahydrobenzo[4,5]indene

The title compound 1-（4-chlorophenyl）-2-cyano-3-amino-3a-hydroxy-3a,3b,6,7- tetrahydro-benzo[4,5]indene 2, has been synthesized by the reductive cyclization of 2-cyano-3- （4-chlorophenyl）-3-（1-tetralon-2-yl） propionitrile 1 induced by low-valent titanium reagent and its structure was determined by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group C2/c with a = 28.244（7）, b = 14.401（3）, c = 21.245（3）A,β= 115.71（2）°, V = 7786（3）A^3, Mr= 696.13, Dc = 1.188 g/cm^3, Z = 8,μ（MoKα） = 0.208 mm^-1, F（000） = 2916, R = 0.0783 and wR = 0.2350. X-ray analysis reveals that the five-membered ring （C（7）～C（l l）） adopts an envelop conformation, while the six-membered ring （C（10）～C（14）, C（19）） has a half-chair conformation. Meanwhile, intermolecular H-bond interactions result in the formation of polymer.

Crystal Structure of Indenyl-3-indenyl

The crystal structure of the title compound (C18H16, Mr = 232.31) has been determined by single-crystal X-ray diffraction. The crystal is of monoclinic, space group P21/n with a = 6.3449(9), b = 6.6297(9), c = 15.727(2) ? ?= 94.338(3), ?= 0.71073 ? ?= 0.066 mm-1, V = 659.66(16) 3, Z = 2, Dc = 1.170 g/cm3 and F(000) = 248. The structure was refined to R = 0.0560 and wR = 0.1426 for 771 observed reflections with I > 2(I). X-ray diffraction analysis reveals that the title compound is a dimer of indene.

TfOH/Fe（OTf）3 Cocatalyzed Reaction of Arylallenes with Alcohols for Structurally Diverse Indene Derivatives

The indene moiety is an important unit because of its presence in many chemical catalysts, functional materials and biologically relevant molecules. Herein, we report a facile reaction of arylallenes with benzylic or allylic alcohols through TfOH/Fe（OTf）3 cocatalyzed cleavage of sp3 carbon-oxygen. In the presence of 5 mol% TfOH and 5 mol% Fe（OTf）3, a range of arylallenes undergo carbocation initiated cyclization reaction with alkyl alcohols to give structurally diverse polysubstituted indenes in good to excellent yields. H2O is the sole byproduct that makes this transformation highly atom-economic and environmentally benign.

Reductive Coupling of Aryl Halides via C-H Activation of Indene

This paper describes the first case of a reductive coupling reaction with indene,a non-heteroatom olefin used as a reducing agent.The scope of the substrate is wide.The homo-coupling,cross-coupling,and synthesis of 12 and 14-membered rings were realized.The control experiment,indene-product curve and density functional theory calculations showed that the η^(3)-palladium indene intermediate was formed by C-H activation in the presence of cesium carbonate.We speculate that the final product was obtained through a Pd(IV)intermediate or aryl ligand exchange.In addition,we excluded the formation of palladium anion(Pd(0)^(-))intermediates.

Efficient One-step Synthesis and Properties of Photochromic Diarylethenes Having an Indene Bridging Unit

Two novel isomeric photochromic diarylethenes with an indene bridging unit have been prepared by a simple and efficient one-step synthesis method. Their properties, including photochromic behavior, fluorescent properties and fatigue resistance, have been investigated. These two isomeric compounds showed photochromic back-and-forth reactions with ultraviolet and visible light both in solution and in PMMA film. Their ring-open forms exhibited appreciable fluorescence, which was quenched by the ring-closed forms. All results indicated that diarylethenes derivatives with indene-aryl bridges exhibited rather high fatigue resistance and good thermally irreversible photochromic properties.

Mechanistic Studies on Propargyl Alcohol-Tethered Alkylidenecyclopropane with Aryldiazonium Salt Initiated by Visible Light

This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo-induced single-electron-transfer(SET)of an electron donor-accepter(EDA)complex.The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate.In these two processes,another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.The mechanistic studies have been carried out by control experiments,kinetic and spectroscopic analyses,deuterium labeling experiments to support these two chain processes.

Convenient Synthesis of Indene Derivatives via Intramolecular Friedel-Crafts Cyclization of Tetraaryl Substituted 1,3-Butadienes

A convenient and efficient method for the highly regioselecfive synthesis of indene derivatives 4 and 5 from tetraaryl substituted 1,3-butadienes 3 was described. The method involves an intramolecular Friedel-Crafts cyclization and a corresponding double-bond positional shift of isomers 4 and 5 in the presence of different Lewis acids under mild conditions with higher than 90% yields.