Allyltin Reagents Research Articles

Palladium-Catalyzed Stereoselective C-F Bond Vinylation and Allylation of Tetrasubstituted gem-Difluoroalkenes via Stille Coupling: Synthesis of Monofluorinated 1,3- and 1,4-Dienes.

We herein describe a Pd-catalyzed stereoselective C-F bond vinylation and allylation reaction of tetrasubstituted gem-difluoroalkenes for the synthesis of valuable monofluorinated 1,3- and 1,4-dienes with excellent diastereoselectivities. Different from previously used Pd(PPh3)4, a catalytic system involving Pd(0) and dppe as the ligand was developed for Stille-type cross-coupling between gem-difluoroalkenes and vinyl- and allyltin reagents.

Forging C–C Bonds with Hindered Nucleophiles and Carbonyl Electrophiles: Reactivity and Selectivity of Allylic Tin Reagents/n-BuLi

Under activation with n-BuLi, trialkylstannanes containing crotyl-, geranyl-, and phenyldienylmethyl appendages were reacted with efficiency and selectivity to various ketone and enone electrophiles with low reactivity. The straightforward process gives access to tertiary alcohols that are vicinal to quaternary carbons. With α,α′-dimethoxy-γ-pyrone, on the other hand, the grafting of a dienyl side chain was effected to prepare dienyl α′-methoxy-γ-pyrone in a stereo- and regioselective and convergent manner. Furthermore, the advantages of this route were highlighted for the preparation of organolithium species at low temperature with the formation of a minimum amount of salts. Synthetic manipulations were demonstrated to illustrate the potential of the chemistry for constructing acyclic and cyclic terpene scaffolds.

Radical Cyclization Followed by the Fragmentation of Carbonyl Compounds: Effect of an α-Benzoyl Group.

To study a recently developed radical cyclization reaction followed by a fragmentation process in more detail, a series of α-benzoyl carbonyl compounds were prepared, including precursors with aldehyde and ketone moieties. Initiated by tributyltin hydride and AIBN, radical cyclization followed by fragmentation proceeded to give the desired carbonyl translocation products in 4-benzoyl-5-pentanal, 4-benzoyl-5-pentanone, 5-benzoyl-6-hexanal, and 5-benzoyl-6-hexanone radical systems. In comparison with early reports on radical cyclization reactions of α-oxy carbonyl compounds, neither a geminal dialkyl effect nor a conformationally rigid system was required to give the desired carbonyl translocation products. This effect clearly proves that a benzoyl group serves as a protecting group in these radical processes, which not only enhances cyclization efficiency but also increases the rate of the fragmentation step, eventually producing the desired carbonyl translocation products. These observations provide an alternative point of view in the field of radical cyclization reactions. Since the fragmentation step could be enhanced by appropriately positioning an α-benzoyl group, these four radical processes could be used to convert the naturally occurring d-sugars, such as d-pentoses and d-hexoses, into rare deoxy-l-sugars. Furthermore, a cascade radical process involving radical cyclization and fragmentation followed by addition to the allyltin reagent was developed and is reported herein.

不斉点にカルバミン酸エステルを導入したアリルスズ試剤からの二方1,4-遠隔不斉誘導反応

不斉点にカルバミン酸エステルを導入したアリルスズ試剤からの二方1,4-遠隔不斉誘導反応

キラル置換基をもつアリルスズ試剤とアルデヒドとの1,5-遠隔不斉誘導反応の制御

キラル置換基をもつアリルスズ試剤とアルデヒドとの1,5-遠隔不斉誘導反応の制御

Reactivity and Selectivity of Organotin Reagents in Allylation and Arylation: Nucleophilicity Parameter as a Guide

By using the inverse concept of electrophilicity and nucleophilicity and with two different available equations from the literature for electrodonating power, the global nucleophilicity index (N) of 99 organotin and 10 allylmetal reagents (metal = Mg, Zn, B, In, Si) have been calculated at the B3LYP/LAN2DZ, 6-31G(d) level of theory. The nucleophilicity scale is validated by the good linear fit between N-values of para-substituted arylstannanes and Hammett σp values of the substituents on the aryl ring. The global nucleophilicity index N has been utilized successfully to explain the reactivity of aryltin and allyltin reagents, to understand the effect of substituents directly attached to tin and those attached on the transferable group, and to rationalize the effect of solvents on reactivities of organotin reagents. The local nucleophilicity index value (Nk-) proved to be a useful local descriptor. The Nk- values at the α- and γ-position in various allylmetal reagents (metal = Mg, Sn, Zn, In, B, Si) have b...

Enantioselective Addition of Allyltin Reagents to Amino Aldehydes Catalyzed with Bis(oxazolinyl)phenylrhodium(III) Aqua Complexes

Bis(oxazolinyl)phenylrhodium(III) aqua complexes, (Phebox)RhX2(H2O) [X = Cl, Br], were found to be efficient Lewis acid catalysts for the enantioselective addition of allyl- and methallyltributyltin reagents to amino aldehydes. The reactions proceed smoothly in the presence of 5–10 mol % of (Phebox)RhX2(H2O) complex at ambient temperature to give the corresponding amino alcohols with modest to good enantioselectivity (up to 94% ee).

ChemInform Abstract: Binary 1,4‐Asymmetric Induction Toward Imines from a Single Allyltin Reagent with a Chiral Oxygen Functional Group.

AbstractThe stereochemical outcome of the reaction can be controlled by the Lewis acid.

Binary 1,4-asymmetric induction toward imines from a single allyltin reagent with a chiral oxygen functional group

A single allyltin reagent possessing a chiral oxygen functional group afforded each diastereomeric product in the reaction with N-sulfonylimines promoted by appropriate Lewis acids in a binary stereoselective manner. InCl 3 selectively provided the syn-1,4-amino alcohol derivatives, while BF 3 and TiCl 4 gave the anti-products preferentially.

ChemInform Abstract: “Propylene Spaced” Allyl Tin Reagents: A New Class of Fluorous Tin Reagents for Allylations under Radical and Metal-Catalyzed Conditions.

Abstract A new generation of propylene-spaced fluorous allyltin reagents [(Rf(CH 2 ) 3 ) 3 SnCH 2 CHCH 2 ] is described. These succeed in radical allylations where their lower homologs (ethylene-spaced) fail, and they provide improved performance in transition metal catalyzed allylations. The reagents and byproducts are readily separated by simple fluorous-organic liquid-liquid or solid-liquid extractions.

ChemInform Abstract: Contrasting Regiochemistry in Thermal and Photochemical Allylstannations of 1,2-Naphthoquinone.

1,2-Naphthoquinone with γ-substituted allyltin reagents undergoes both thermal and photochemical reactions, which show the opposite regioselectivities to each other. The both reactions are supposed to proceed via the initial 1,2-addition, which occurs at the γ-position of the allyltin in the thermal reaction and at the less hindered α-position in the photoreaction, followed by the [3,3] allylic migration.

Reaction of carbon nucleophiles with alkylideneindazolium and alkylideneindolium ions generated from their 3-(1-arylsulfonylalkyl) indazole and indole precursors

Lewis acid promoted elimination of p-toluenesulfinc acid from sulfonyl indazoles and sulfonyl indoles generates the corresponding iminium ion that reacts with allyltin reagents, silyl enol ethers, silyl ketene acetals and electron-rich aromatics leading to functionalized indazole and indole derivatives.

ChemInform Abstract: Binary 1,4‐Asymmetric Induction from a Single Allyltin Reagent with a Chiral Nitrogen Functional Group Toward Aldehydes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Binary 1,4-asymmetric induction from a single allyltin reagent with a chiral nitrogen functional group toward aldehydes

Using a single allyltin reagent with a chiral nitrogen functionality, binary and remote asymmetric induction was realized toward various aldehydes. Either syn- or anti-1,4-amino-alcohols were selectively obtained with the use of Yb(OTf) 3 or SnCl 4, respectively. The structures of both diastereomers were identified by means of X-ray analysis.

A New Route to Polymer-Supported Allyltin Reagents

A New Route to Polymer-Supported Allyltin Reagents

Preparation of Allyltin Reagents Grafted on Solid Support: Clean and Easily Recyclable Reagents for Allylation of Aldehydes

The preparation of polymer-supported allyltin reagents was shown to be possible for both unfunctionalized and functionalized allyl units. These reagents were treated with aldehydes in the presence of cerium(III) or indium(III) salts to afford high yields of homoallylic alcohols, practically uncontaminated with organotin residues (less than 5 ppm). Some mechanism aspects are briefly discussed and the potential for regeneration and reuse of these supported reagents is pointed out.

Three-Component Synthesis of Homoallylic Amines Promoted by Carboxylic Acids

A highly selective, three-component reaction promoted by carboxylic acids for the synthesis of homoallylic amines has been developed. By using maleic acid or trifluoroacetic acid as a promoter, the reaction between a variety of aldehydes, aromatic amines, and allyltin reagents proceeds smoothly to afford the corresponding homoallylic amines in moderate to quantitative yields under mild conditions.

Studies on Tellurium‐Containing Heterocycles. Part 25. 1‐Allylation of 2‐Benzotelluropyrylium Salts and 2‐Benzoselenopyrylium Salts by Means of Allyltin Reagents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly Efficient Binary and Remote Asymmetric Induction from a Single Allyltin Reagent with a Chiral Carbamate Moiety.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF.

1-Allylation of 2-Benzotelluropyrylium Salts and 2-Benzoselenopyrylium Salts by Means of Allyltin Reagents

3-tert-Butyl-2-benzotelluropyrylium salt (1) reacts with an equal amount of allyltributyltin to afford l-allyl-3-tert-butyl-1H-isotellurochromene (8a) in 93 % yield. Similarly, 1-allyl-1H-isotellurochromenes (9) and isoselenochromenes (10, 11) were prepared from the corresponding pyrylium salts (2-4) in moderate to good yields.