Insertion of an Isolable Dialkylstannylene into C–Cl Bonds of Acyl Chlorides Giving Acyl(chloro)stannanes

The reactions of isolable dialkylstannylene <b>1</b> with 1-adamantanoyl, 2,2-dimethylpropanoyl, benzoyl, and substituted benzoyl chlorides afford the corresponding acyl­(chloro)­stannanes in good yields. Similar reactions with more reactive acetyl and propanoyl chlorides do not give the corresponding insertion products but the corresponding dichlorostannane by the overreaction. The benzoyl­(chloro)­stannane reacts with acetyl chloride to afford the corresponding 1,2-dione and the dichlorostannane quantitatively. Acyl­(chloro)­stannanes obtained were fully characterized by multinuclear NMR spectroscopy, high-resolution mass spectrometry, and by single-crystal X-ray diffraction studies

Stereoselective Formation of Eight-Membered Rings by Radical Cyclization of Silylenedioxy-Tethered Bis-methacrylate Derivatives

Radical-initiated addition of CCl₄, Cl₃CBr, PhSH, and (TMS)₃SiH to (bisisopropyl)­silylene­dioxy-tethered bis-methacrylate derivatives gives the corresponding eight-membered ring cyclic adducts stereoselectively. Hydrolysis of halo-substituted cyclic adducts with HCl in methanol affords the corresponding valerolactones, and the stereochemistry was determined by the X-ray crystallography on a dibromobenzoate derivative. DFT calculation on the eight-membered radical intermediate offers a plausible rationale for the stereoselectivity of the reaction

Reactions of an Isolable Dialkylstannylene with Carbon Disulfide and Related Heterocumulenes

The reaction of isolable dialkylstannylene <b>1</b> with an excess amount of CS₂ produces an isomeric mixture of 3,3′-distanna-2,2′,4,4′-tetra­thia­bicyclo­butylidene <b>8</b> and 3,7-distanna-2,4,6,8-tetra­thia­bicyclo­[3.3.0]­oct-1(5)-ene <b>9</b> with a ratio depending on the reaction conditions. Compounds <b>8</b> and <b>9</b> are separated by column chromatography and characterized by NMR spectroscopy and X-ray crystallography. Detailed investigation of the reaction has revealed that the initial product is <b>8</b>, which isomerizes to <b>9</b> irreversibly under the catalytic influence of <b>1</b> as a Lewis acid. The above view is supported by the theoretical DFT calculations. Treatment of <b>1</b> with ArNCO [Ar = 2,6-<i>i</i>Pr₂C₆H₃] affords the corresponding carbamoyl­(hydroxyl)­stannane <b>11</b> via the hydrolysis of the corresponding sila­aziridinone formed by the [1 + 2] cycloaddition reaction of <b>1</b> with the NC double bond of the isocyanate. Stannylene <b>1</b> reacts with ArNCS, giving a mixture of complex products, while <b>1</b> does not react with CO₂

Synthesis of δ-Carbolines via a Pd-Catalyzed Sequential Reaction from 2-Iodoanilines and <i>N</i>-Tosyl-enynamines

A facile Pd-catalyzed sequential reaction has been developed for the synthesis of δ-carbolines from 2-iodoanilines and <i>N</i>-tosyl-enynamines. This protocol involves Larock heteroannulation/elimination/electrocyclization/oxidative aromatization cascade sequences and allows access to multisubstituted δ-carbolines in moderate to good yields

Reactions of an Isolable Dialkylstannylene with Propynoates and Benzyne

The reactions of stable monomeric dialkylstannylene <b>1</b> with methyl and ethyl propynoates give the corresponding 1:2 adducts, alkenyl­(alkynyl)­stannane <b>2</b> and <b>3</b> in high yields, while <b>1</b> does not react with parent acetylene or common mono- and disubstituted acetylenes such as phenylacetylene, trimethylsilylacetylene, diethyl 2-butynedioate, etc. Notably, <b>2</b> and <b>3</b> have the <i>Z</i>-configuration of the alkenyl moieties, in contrast to similar adducts obtained by the known reactions of silylenes with terminal acetylenes. It is suggested that the formation of a carbonyl oxygen-coordinate cyclic zwitterion as a key intermediate is essential for the reactions. Stannylene <b>1</b> adds to in situ generated benzyne, forming a 1:1 adduct having a unique 3-stanna-1-silaindane ring system

Reactions of an Isolable Dialkylstannylene with Propynoates and Benzyne

The reactions of stable monomeric dialkylstannylene <b>1</b> with methyl and ethyl propynoates give the corresponding 1:2 adducts, alkenyl­(alkynyl)­stannane <b>2</b> and <b>3</b> in high yields, while <b>1</b> does not react with parent acetylene or common mono- and disubstituted acetylenes such as phenylacetylene, trimethylsilylacetylene, diethyl 2-butynedioate, etc. Notably, <b>2</b> and <b>3</b> have the <i>Z</i>-configuration of the alkenyl moieties, in contrast to similar adducts obtained by the known reactions of silylenes with terminal acetylenes. It is suggested that the formation of a carbonyl oxygen-coordinate cyclic zwitterion as a key intermediate is essential for the reactions. Stannylene <b>1</b> adds to in situ generated benzyne, forming a 1:1 adduct having a unique 3-stanna-1-silaindane ring system

Reactions of an Isolable Dialkylsilylene with Carbon Dioxide and Related Heterocumulenes

An isolable dicoordinate dialkylsilylene, 2,2,5,5-tetrakis­(trimethylsilyl)­silacyclopentane-1,1-diyl (<b>6</b>), was found to react with CO₂ and ArNCX (X = O, S) smoothly to give the corresponding bis­(silyl)­carbonate, 4-imino-1,3-dioxasiletane and 4-imino-1,3-dithiasiletane derivatives in high yields, respectively. The molecular structures of these products were determined by X-ray crystallography. All these reactions are parallel to those of a hypercoordinate silylene with η⁵-pentamethylcyclopentadienyl ligands, decamethylsilicocene, reported by Jutzi et al. and are suggested to involve similarly the formation of the corresponding SiX doubly bonded compounds (X = O, S) at the initial steps. Mechanistic details of the multistep reaction of a model dialkylsilylene with CO₂ were investigated using DFT calculations