Phenyl stannyl

Fig. 9. Synthesis of methylphenyl(2-phenyl)stannyl-transition metal complexes I8).

In the first systematic study on nucleophilic substitutions of chiral halides by Group IV metal anions, Jensen and Davis showed that (S )-2-bromobutane is converted to the (R)-2-triphenylmetal product with predominant inversion at the carbon center (Table 5)37. Replacement of the phenyl substituents by alkyl groups was possible through sequential brominolysis and reaction of the derived stannyl bromides with a Grignard reagent (equation 16). Subsequently, Pereyre and coworkers employed the foregoing Grignard sequence to prepare several trialkyl(s-butyl)stannanes (equation 17)38. They also developed an alternative synthesis of more hindered trialkyl derivatives (equation 18). 

Benzyne, which is generated in situ from 2-(trimethylsilyl)phenyl triflate and KF, acts as an alkyne congener in distannation in the presence of palladium-/ r/-alkyl isocyanide complex.157 A variety of substituted benzyne derivatives inserts into the Sn-Sn bond to give l,2-bis(stannyl)benzenes (Equation (59)). The reaction fails to occur in the presence of other palladium catalysts such as Pd(PPh3)4. 

Methyl-1,2,4-diazaphosphole (6) is metallated by butyllithium selectively in the 5-position <87JOM(3l9)49>. From the subsequent reaction with an electrophilic element halide, 5-methyl-, 5-stannyl-, and 5-boryldiazaphospholes (7) are obtained <87JOM(3l9)49,87TH 422-01 >. Catalytic amounts of potassium t-butoxide in acetonitrile-i/j effect an H/D-exchange, fast in the 5-position and slow in the 3-position of 1-phenyl-1,2,4-diazaphosphole <87JOM(3l9)49>. 

Poly(pyrido[3,4- ]pyrazine vinylene) 693 has been synthesized via condensation of 3,4-diamino-2,5-dibtomopyridine 691 with l,2-bis[3-(2 -ethylhexyloxy)phenyl]-ethane-l,2-dione 692 followed by coupling with l,2-bis(tri- -butyl-stannyl)ethylene in DMF at 110°C in the presence of tetrakis(triphenylphosphine)palladium. The vinylene polymer 693 showed improved stability toward photooxidation compared with similar polymers with purely aliphatic side chains and also had smaller band gaps (Equation 58) <2002SM(131)53>. 

The mechanism of this transformation is outlined in Scheme 38 and each step has important features. In step 1, the tributyltin radical abstracts the radical precursor X. A possible side reaction, the addition of the tributyltin radical to the allylstannane, is much slower than comparable additions to activated alkenes. Even if this addition occurs, the stannyl radical is simply eliminated to regenerate the starting materials. Thus, for symmetric allylstannanes, this reaction is of no consequence. As a result, the range of precursors X that can be used in allylation is more extensive than in the tin hydride method. Even relatively unreactive precursors like chlorides and phenyl sulfides can be used if they are activated by adjacent radical-stabilizing groups. 

Alkenyl(phenyl)iodonium salts have attracted a significant interest recently as stable and readily available powerful alkenylating reagents. Several convenient, general procedures for the stereoselective synthesis of alkenyliodonium salts from silylated or stannylated alkenes and the appropriate hypervalent iodine reagents are known [5]. The chemistry of alkenyliodonium salts has been extensively covered in several recent reviews [42 - 45]. 

Direct C-l deprotonation-lithiation occurs on treatment of the O-benzyl-ated or -silylated glycals with strong bases such as tert-butyllithium at low temperatures, and the vinyllithiums (such as 120) can subsequently be stannylated with tributylstannyl chloride.135 Otherwise, compound 121 can be produced from S-phenyl tetra-C-benzyl-l-thio-/f-D-glucopyranoside via sulfone 122 by treatment with tributylstannane and a radical initiator.132... 

The structures of both the phenyl and 2,5-dimethylphenyl tin clusters were established by single-crystal X-ray diffraction. Under similar conditions, toluene was stannylated to produce a mixture of organotin compounds. Bromination of this mixture yielded 3-bromotoluene and 4-bromotoluene in a 2 1 ratio, with trace amounts of 2-bromotoluene. Similarly, PhBr was produced upon treatment of the phenyltin product with aqueous Br2. No applications of the stannylation reactions have yet been reported. 

Another application of the direct alkylation of metal-14 anions is the synthesis of polymer-supported organotin hydrides. These were prepared by the reaction of stannyl group was separated from the phenyl ring of polystyrene by two, three or even four carbon spacers. These polymers were found to contain 0.8-1.4 mmol of Sn-H per gram. The reducing ability of the polymer-supported organotin hydrides was monitored by reactions with haloalkanes (Scheme 22)142. 

The first alkynyliodonium salt, (phenylethynyl)phenyliodonium chloride, synthesized in low yields from (dichloroiodo)benzene (3) and lithium phenylacetylide (equation 1), was reported in 196526. This chloride salt is unstable and readily decomposes to a 1 1 mixture of chloro(phenyl)acetylene and iodobenzene. It was not until the 1980s, however, that alkynyliodonium salts became generally available. This was made possible by the introduction of sulfonyloxy-/l3-iodanes as synthetic reagents46 and by the recognition that iodosylbenzene (4) can be activated either with boron trifluoride etherate or with triethy-loxonium tetrafluoroborate31. These reagents are now widely employed for the conversion of terminal alkynes and their 1-silyl and 1-stannyl derivatives to alkynyliodonium salts (equations 2 and 3). A more exhaustive survey of iodine(III) reagents that have been... 

Hydrostannation of alkynes is one of the simplest and direct routes to vinylstannanes which have great versatility as building blocks in syntheses. However, a variety of regio and stereo isomers are usually formed.17-22 Until now, the selectivities are controlled by using different types of tin hydrides described above.26,92 For aryl-subsutituted alkynes, radical stannylation leads to the regioselective formation of the /3-adducts but with poor stereoselectivity. The addition of bulky tris[(phenyl dimethylsilyl)methyl]tin hydride indicates that these reactions take place with complete kinetic or thermodynamic stereoselectivity (Equation (30)).93... 

A radical approach to cyclization is offered by the intramolecular homolytic substitution (ShO reaction at a silicon center. Reaction of phenyl bromoacetate with a stannylated silyl homoallyl ether under atom transfer conditions provides cyclic alkoxysilanes (Equation (119)).2... 

Methyl trimethylsilyl tellurium and phenyl trimethylsilyl tellurium exchanged the organyltelluro group for halogen in reactions with silyl, germyl, stannyl and plumbyl halides2. 

Vinyllithiums of type 663 (R2 = R3 = H) reacted with primary alkyl bromides, carbonyl compounds, carbon dioxide, DMF, silyl chlorides, stannyl chlorides, disulfides and phenylselenyl bromide142,970-979. Scheme 173 shows the synthesis of dihydrojasmone 669 from the corresponding 1,4-diketone. a-(Phenylsulfanyl)vinyllithium 665, prepared from phenyl vinyl thioether, reacted with hexanal and the corresponding adduct 666 was transformed into its acetoacetate. This ester 667 underwent a Carrol reaction to produce the ketone 668, which was transformed into the cyclopentenone 669 by deprotection either... 

Hydrostannation of (l-alkynyl)carbene chromium complexes involves addition to the M = C bond as well as to the C=C bond and is strongly influenced by the substituent at the alkynyl moiety. By the bulky trimethyl-silyl group of compound lg, a 1,1-addition to the carbene carbon atom is promoted with formation of a densely functionalized 1,3-heterobimetal lie propargyl reagent 93 containing both a stannyl and a silyl group. A 3,1-addition is observed with phenyl derivative la and also the vinyl compound lo, which leads to production of an allene 94 and 95, respectively (Scheme 31).111... 

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. 

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