Tributyltin Hydride Research Articles

A One-Pot, Stereoselective Synthesis of (Z)-1,2-disubstituted Vinyl Sulfides by Sequential Hydrostannylation and Stille reaction of Acetylenic Sulfides with Tributyltin Hydride and then with aryl iodides

( Z)-1,2-Disubstituted vinyl sulfides can be stereoselectively synthesised in one pot under mild conditions, in good yields, by the palladium-catalysed hydrostannylation of acetylenic sulfides, followed by Stille coupling with aryl iodides.

Palladium(II)-Catalyzed Isomerization of Olefins with Tributyltin Hydride

A new efficient method for the synthesis of geometrically pure (E)-alkenes from (Z)-alkenes is described. The reaction of aryl- or alkyl-substituted (Z)-alkenes with tributyltin hydride and triethylamine in the presence of a catalytic amount of palladium acetate afforded the corresponding (E)-alkenes in good yields.

Catalysis of Stannane-Mediated Radical Chain Reactions by Benzeneselenol

The discovery and development of the catalysis of stannane-mediated radical chain reactions by benzeneselenol, generated in situ by reduction of diphenyl diselenide with tributyltin hydride, are described. The catalytic sequence is discussed in terms of polarity reversal catalysis of radical chain reactions, and applications to synthesis are presented. These include the prevention of numerous radical rearrangement reactions, the ability to intervene in certain multistep radical rearrangements, especially aryl and vinyl radical cyclizations, at intermediate stages with advantages to the product profile, and the effective trapping of allyl-, benzyl-, and cyclohexadienyl-type radicals, permitting inter alia the isolation of aryl cyclohexadienes and their application in synthesis.

A One-Pot, Stereoselective Synthesis of 1,3- and 1,4-Dienyl Sulfones by Hydrostannylation-Stille Tandem Reaction of Tributyltin Hydride with Acetylenic Sulfones and Alkenyl or Allylic Halides

1,3-Dienyl and 1,4-dienyl sulfones can be stereoselectively synthesized in one pot under mild conditions, in good yields, by the palladium-catalyzed hydrostannylation of acetylenic sulfones, followed by Stille coupling with alkenyl or allylic halides, respectively.

Synthesis of a Spore Surface Pentasaccharide of Bacillus anthracis

AbstractAn analogue 2 of the pentasaccharide 1 found on the spore surface protein BclA of Bacillus anthracis was synthesized by a (3+2) glycosylation approach. A robust building block for 3‐linked α‐rhamnose is presented. Benzoate groups were used to ensure α‐selectivity for the rhamnose units. A radical‐initiated reduction with tributyltin hydride was shown to be able to convert the NHTCA group into an acetylated amine as well as an azido group into a free amine on one strike. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Antineoplastic Agents. 550. Synthesis of 10b(S)-Epipancratistatin from (+)-Narciclasine,1

By means of a five-step reaction sequence, narciclasine (2a), isolated from Narcissus sp., was converted to 10b(S)-epipancratistatin (3a) in 5.7% overall yield. The key step entailed a radical-initiated 10b,1 C-O cleavage employing tributyltin hydride to yield a B/C cis ring juncture (3b). Biological evaluation of 10b(S)-epipancratistatin (3a) provided evidence that antineoplastic activity was reduced by a factor of 10 when the B/C trans juncture was replaced with a B/C cis ring juncture.

A highly efficient synthesis of (Z)‐1‐aryl‐2‐silyl‐1‐ stannylethenes and their conversion to (E)‐2‐ arylethenyl‐, (Z)‐2‐(2‐pyridyl)ethenyl‐ and allenyl‐silanes

AbstractA Pd(dba)2–P(OEt)3 combination allowed the silastannation of arylacetylenes, 1‐hexyne or propargyl alcohols with tributyl(trimethylsilyl)stannane to take place at room temperature, producing (Z)‐2‐silyl‐1‐stannyl‐1‐substituted ethenes in high yields. Novel silyl(stannyl)ethenes were fully characterized by 1H‐, 13C‐, 29Si‐ and 119Sn‐NMR as well as infrared and mass analyses. Treatment of a series of (Z)‐1‐aryl‐2‐silyl‐1‐stannylethenes and (Z)‐1‐(3‐pyridyl)‐2‐silyl‐1‐stannylethene with hydrochloric acid or hydroiodic acid in the presence of tetraethylammonium chloride (TEACl) or tetrabutylammonium iodide (TBAI) led to the exclusive formation of (E)‐trimethyl(2‐arylethenyl)silanes with high stereoselectivity. A similar reaction of (Z)‐1‐(2‐anisyl)‐2‐silyl‐1‐stannylethene also produced E‐type trimethyl[2‐(2‐anisyl)ethenyl]silane, while (Z)‐trimethyl [2‐(2‐pyridyl)ethenyl]silane was produced exclusively from (Z)‐1‐(2‐pyridyl)‐2‐silyl‐1‐stannylethene. Protodestannylation of (Z)‐1‐[hydroxy(phenyl)methyl]‐2‐silyl‐1‐stannylethene with trifluoroacetic acid took place via the β‐elimination of hydroxystannane, providing trimethyl(3‐phenylpropa‐1,2‐dienyl)silane quite easily. The destannylation products were also fully characterized. Copyright © 2007 John Wiley & Sons, Ltd.

Reductively induced homolytic carbon–carbon bond cleavage in Co(CO) 3(PPh 3)(COCF 3)

The chemical or electrochemical reduction of the trifluoroacetyl complex Co(CO) 3(PPh 3)(COCF 3) involves a single electron transfer yielding trifluoromethyl radical and an anionic cobalt carbonyl complex. The mechanism is proposed to involve electron transfer followed by initial dissociation of either a carbonyl or phosphine ligand from the 19-electron [Co(CO) 3(PPh 3)(COCF 3)] − anion. The resulting 17-electron intermediate undergoes subsequent one-electron reductive elimination of trifluoromethyl radical by homolytic cleavage of the carbon–carbon bond of the trifluoroacetyl group. The CF 3 radical can be trapped by either benzophenone anion, forming the anion of α-(trifluoromethyl)benzhydrol, or Bu 3SnH, yielding CF 3H. The ultimate organometallic product is an 18-electron anion, either [Co(CO) 4] − or [Co(CO) 3(PPh 3)] −, depending upon which ligand is initially lost. Fluorine-containing products were identified and quantitated by 19F NMR while cobalt-containing products were determined by IR.

Insertion of CO2into a palladiumallyl bond and a Pd(ii) catalysed carboxylation of allyl stannanes

The complex 2,6-bis[(di-t-butylphosphino)methyl]phenyl allyl palladium (PCP(tBu)Pd-allyl, 3) reacts with CO(2) in a very fast insertion reaction to give the corresponding butenoate complex. The reaction is thought to occur via a cyclic six-membered transition state (7), where the gamma-carbon of the allyl group is linked up with the CO(2)-carbon. A group of related PCP complexes were investigated as catalysts for the carboxylation of tributyl(allyl)stannane. A catalytic cycle is proposed for this reaction where the rate determining step is the transmetallation between tin and palladium. The carboxylation reaction is faster using less sterically crowded catalysts whereas the electron richness of the palladium complexes seems less important for reactivity. Thus, there was no apparent difference in reactivity between 2,6-bis[(di-phenylphosphino)methyl]phenyl palladium triflouroacetate (13) and resorcinolbis(diphenyl)phosphinite palladium triflouroacetate (10). Both of these complexes give high turnovers for the carboxylation of tributyl(allyl)stannane (80% in 16 h using a ca. 5% catalyst loading and 4 atm CO(2) pressure). On the other hand complex 3 was inactive in the catalytic carboxylation reaction.

A Facile Synthesis of 1,1-Disubstituted Isoindoline Derivatives by Intramolecular Iodoamination of 2-Vinylbenzylamine Derivatives

The intramolecular iodoamination of N-(2-vinylbenzyl)acetamide derivatives, derived from α-substituted 2-vinylbenzonitriles in two steps, afforded the corresponding 2-acetyl-1 -iodomethylisoindoline derivatives, which were transformed into the 1-methyl or 1-sulfenylmethyl derivatives by tributyltin hydride reduction or substitution by sodium thiolates, respectively, in reasonable yields.

Amides as precursors of imidoyl radicals in cyclisation reactions

Amides have been successfully used as precursors of imidoyl radicals for radical cyclisation. The amides have been converted to imidoyl selanides via reaction with phosgene to yield imidoyl chlorides followed by reaction with potassium phenylselanide. Imidoyl selanides were reacted with tributyltin hydride (Bu 3SnH) as the radical mediator with triethylborane or AIBN as initiators to yield imidoyl radicals for cyclisation reactions. Imidoyl radicals have been cyclised onto alkenes to yield 2,3-substituted-indoles and -quinolines and also onto pyrroles and indoles to give bi- and tricyclic heteroarenes.

Synthesis of 3-oxatricyclo[4.4.0.02,7]decene derivatives

Unsaturated haloethers of norpinane structure were prepared by reaction of N-iodo-and N-bromosuccinimides with 1-phenyltricyclo[4.1.0.02,7]-heptane in the presence of unsaturated propargyl or allyl alcohol. The iodopropargyloxy derivative underwent reductive 6-exo-cyclization when treated with tributyltin hydride resulting in 5-methylene-3-oxa-2-phenyltricyclo[4.4.0.02,7]decane, and the iodoallyloxy derivative on heating in the presence of benzoyl peroxide suffered isomerization into 5-iodomethyl-3-oxa-2-phenyltricyclo[4.4.0.02,7]decene. Bromopropargyloxy and bromoallyloxy derivatives failed to undergo the reductive cyclization under the treatment with a system cobaloxime(III)-sodium borohydride, but suffered hydrogenetion at the multiple carbon-carbon bond.

Sequential Baylis–Hillman reaction and radical cyclization of furanose derivatives: expeditious approach to enantiopure benzo-fused nine-membered oxacycles

A regioselective 9- endo- trig aryl radical cyclization of d-glucose derived diastereomeric Baylis–Hillman reaction products with Bu 3SnH led to highly functionalized tricyclic benzannulated ethers incorporating cis- and trans-9,5 bicyclic systems in good yields. Degradation of one of the products afforded an enantiopure multifunctionalized benzoxonine derivative.

1,1,3,3-Tetrakis(alkylthio)-1,3-dilithio-2-silapropanes: Useful reagents for the synthesis of polysilacycloalkanes via dianionic ring formation

Treatment of 1,1,3,3-tetrakis(alkylthio)-2-silapropanes with t-BuLi in THF at -40 °C generated 1,1,3,3-tetrakis(alkylthio)-1,3-dilithio-2-silapropanes which reacted with various bifunctional chlorosilanes to give the corresponding 4- to 7-membered polysilacycloalkanes in moderate to good yields. Furthermore, double alkylation of the dilithiated silanes with bis(halomethyl)diorganosilanes or dihaloalkanes was found to proceed smoothly giving rise to 1,4-disilacyclohexanes or silacycloalkanes in good yields, respectively, in THF and an aprotic polar co-solvent such as hexamethylphosphoric triamide (HMPA) or 1,1,3,3-tetramethylurea (TMU). The sulfenyl groups in the cyclized products were smoothly removed by radical reduction with tributyltin hydride.

2-Chloroquinazoline. Synthesis and reactivity of a versatile heterocyclic building block

Starting from 2,4-dichloroquinazoline, various methods for the selective removal of the 4-chloro substituent were tested, including catalytic hydrogenation, metal–halogen exchange, metal hydride reduction and reduction with tributyltin hydride—the latter both in a radical and in a Stille-type reaction. Amongst these, the most efficient method was found to be the Stille-type coupling. Furthermore, we have studied the reactivity of 2-chloroquinazoline and found it to act as a versatile building block for the direct introduction of the 2-quinazolinyl moiety.

Palladium-catalyzed synthesis of 3-alkoxysubstituted indoles

Indoles having an electron-donating alkoxy-group in the 3-position were prepared from 1-(2-nitrophenyl)-1-alkoxyalkene derivatives via a palladium-catalyzed reductive N-heteroannulation using carbon monoxide as the ultimate reducing agent. The required starting materials were prepared by a Stille coupling of 2-halonitroarenes with tributyl(1-ethoxyethenyl)stannane or tributyl(3,4-dihydro-2 H-pyran-6-yl)stannane.

One-pot synthesis of heterocyclic compounds initiated by chemoselective addition to β-acyl substituted unsaturated aldehydes with nucleophilic tin complexes

β-Acyl substituted unsaturated aldehydes 1 were revealed to be good precursors for the synthesis of various heterocyclic compounds by the combination with tin nucleophiles. Various 2-monosubstituted pyrroles were prepared in an one-pot procedure via the reductive amination of formyl groups of 1 by using Bu 2SnIH–HMPA complex. One-pot synthesis of heterocycles was carried out initiated by chemoselective reduction of 1 with Bu 3SnH–HMPA complex and the subsequent reaction with heterocumulenes. Furthermore, the one-pot synthesis of nitrogen heterocyclic compounds accompanying chemo-, regio- and diastereoselective carbon–carbon bond formation in side chain moieties was effectively accomplished initiated by the regio- and diastereoselective allylation of the formyl group of 1 with allylic tin species.

Remote Stereocontrol Using (E)‐6‐Hydroxy‐4‐methylhex‐2‐enyl(tri‐n‐butyl)stannane.

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.

Synthesis of 2,4-Disubstituted Piperidines via Radical Cyclization: Unexpected Enhancement in Diastereoselectivity with Tris(trimethylsilyl)silane

A novel approach to 2,4-disubstituted piperidines is reported, involving the radical cyclization of 7-substituted-6-aza-8-bromooct-2-enoates. Cyclization with tributyltin hydride affords the trans piperidines with trans/cis diastereomeric ratios ranging typically from 3:1 to 6:1. Cyclization with tris(trimethylsilyl)silane affords the same products with diastereomeric ratios of up to 99:1 in certain cases. The enhancement in diastereoselectivity results from the selective rearrangement of the minor stereoisomer through a cascade process involving radical cyclization to the piperidine radical, 1,5-radical translocation, and attack of the translocated radical onto the sulfonamide with extrusion of SO2 in a Smiles-type rearrangement. Slower trapping of the piperidine radical by tris(trimethylsilyl)silane compared to tributyltin hydride accounts for the occurrence of the rearrangement cascade in the former case.

Two Efficient Syntheses of Protected 4‐Deoxy‐D‐lyxo‐hexose (4‐Desoxy‐D‐mannose)

The formation of four differently protected 4‐deoxy‐D‐lyxo‐hexose derivatives 7, 8, 12, and 14 is described. In the first procedure, a nucleophilic displacement of the allylic mesylate 4 by hydride was combined with a highly stereoselective osmylation of olefin 6 to afford diol 7. In the second radical procedure, tributyl tin hydride was substituted by the cheap and environmentally friendly hypophosphorous acid as a hydrogen donor in the reduction of xanthate 13 to 4‐deoxy lyxo‐hexose 14.