Stannyl selenide

Alkyl stannyl selenides are also useful nucleophilic selenium reagents. Tri-methylstannyl or tributylstannyl methyl selenides 58 react with halides 59 to produce unsymmetrical selenides 60 in good yields in the presence of a fluoride ion or by treatment with n-butyllithium (Scheme 44) [84]. Tributylstannyl phenyl selenide (61) reacts smoothly with acetals to give monoselenoacetals 62 in the presence of boron trifluoride etherate (Scheme 45 a) [85]. Similar reaction conditions were applied to the regioselective ring opening of epoxides (Scheme 45b) [86]. 

If selenide additions are carried out in the presence of tri- -butylstannane, the radical generated by addition can be reduced by hydrogen abstraction. The chain is then continued by selenide abstraction by the stannyl radical. This leads to nonselenated addition and cyclization products. 

Radical homologation. This tin pinacolate is known to generate trimethyltin radicals at 60° and appears to be superior to tributyltin hydride as a source of stannyl radicals for addition of alkyl halides to O-benzylformaldoxime (equation I).1 Iodides, bromides, and selenides can be used as radical precursors. The same... 

Selenenyl groups can be abstracted from acyl selenides to generate radicals on reaction with stannyl radicals.201 202 203 Normally, some type of stabilization of the potential reaction site is necessary. Among the types of selenides that are generated by selenenyl abstraction are x-sclcncnyl cyanides and a-selenenyl phosphates. 

A-allylic amines are conveniently prepared in high yields by the reaction of azides with allylindium reagents in the presence of sodium iodide at ambient temperature (Equation (74)).307 Stannylation with tributylchloro-stannane occurs exclusively at the a-carbon, yielding allyltributylstannanes (E, Z)-isomerization of the allylic double bond depends largely upon the substitution pattern on the allylic moiety (Equation (75)).26 Allyl and propargyl bromides react with diphenyl diselenides in aqueous media to give allyl and propargyl selenides (Equation (76)).308 309... 

HOMOALLYLIC ALCOHOLS B-Allyldiisopino-campheylborane. Allyl phenyl selenide. Allyltri-/i-butyltin. Chromium(II) chloride. Crotyltrimethylsilane. Diethylftributyl-stannyl)aluminum. (2R,4R)-Pentanediol. Pinacol chloromethaneboronate. Tin-Aluminum. Titanium(lV) chloride. 

The reaction of the lithiated allylic carbanion derived from prenyl selenide with hexamethyldistannane did not lead to the mono a-stannylated allylic selenide but to a bis-stannylated compound. A consecutive Se/Sn exchange, without allylic isomerization, occurred [5] (Scheme 4). The reaction involves a selenophilic attack by Mej SnLi formed in the media. 

Reactions herein significantly differ from most standard nBu SnH-mediated radical transformations that employ a variety of well-known precursors for carbon-centered radicals, including halides, thioacyl moieties, olefins, selenides and sulfides. Most of these potentially useful precursors are sacrificed and lost during the radical reaction and are not available for subsequent manipulations [7]. However, O-stannyl ketyl intermediates conserve the carbonyl oxygen for further functionalization. 

Alkynes can be transformed into alkenylstannanes by reaction with stannyl-cuprates. It is possible to trap the 1,2-dimetallic alkene species with various electrophiles. The analogous vicinal difunctionalization of alkynyl selenides " has also been reported. A route to trisubstituted alkenes from phenylthioacetylene"" starts with cuprate addition, but a 1,2-metal rearrangment is involved. Enamines are obtained from N-ethynyldiphenylamine. The alkenylcopper intermediate is also reactive toward many electrophiles. Silylcupration of functionalized alkynes may lead to cyclic products by virtue of intramolecular alkylation. ... 

Bis[tris(pentailuoropheny])stannyl] sulphide, and the conesponding selenide and telluride, may be prepared by reactions of the type ... 

Selenides s. Silyl-selenides, Stannyl-Seleninic acids... 

Bis(triphenyltin)dihydridobis(methyldiphenylphosphine)plati-num, see Sn-00474 Bis(triphenyltin)oxide, see Sn-00440 >Bis(triphenyltin) sulfide, Sn-00443 Bis(triphenyltin)telluride, Sn-00446 >Bis(tripropyltin) oxide, see Sn-00339 >Bis[tris(2-methyl-2-phenylpropyl)tin] oxide, see Sn-00473 Bis[tris(pentafluorophenyl)germyl]cadmium, Ge-00271 Bis[tris(pentafluorophenyl)germyl] mercury, Ge-00273 Bis[tris(pentafluorophenyl)germyl] selenide, see Ge-00275 Bis[tris(pentafluorophenyl)germyl] sulfide, see Ge-00274 [Bis[tris(pentafluorophenyl)stannyl]]mercury, Sn-00435 Bis[tris(trifluoromethyl)germanium]oxide, see Ge-00064 Bis[tris[(trimethylsilyl)methyl]stannyl]mercury, Sn-00399 Bromo( 7 -2,4-cyclopentadien-1 -yl)lead, Pb-00035 Bromo( 7 -2,4-cyclopentadien-1 -yl)tin, Sn-00086 Bromodimethylstannane, Sn-00022... 

Photonucleophilic aromatic substitution reactions of phenyl selenide and telluride with haloarenes have also been proven to involve the S jlAr mechanism, with the formation of anion radical intermediates. Another photonucleophihc substitution, cyanomethylation, proves the presence of radical cations in the reaction mechanism. Liu and Weiss have reported that hydroxy and cyano substitution competes with photo substitution of fluorinated anisoles in aqueous solutions, where cation and anion radical intermediates have been shown to be the key factors for the nucleophilic substitution type. Rossi et al. have proposed the S j lAr mechanism for photonucleophihc substitution of carbanions and naphthox-ides to halo anisoles and l-iodonaphthalene. > An anion radical intermediate photonucleophilic substitution mechanism has been shown for the reactions of triphenyl(methyl)stannyl anion with halo arenes in liquid ammonia. Trimethylstannyl anion has been found to be more reactive than triphenylstannyl anion in the photostimulated electron- transfer initiation step. 

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