Julio C. Podestá

Synthesis and some reactions of mixed (−)-menthyltin hydrides

Abstract The synthesis and physical properties of dineophyl(−)menthyltin ( 4 ) and methylneophyl (−)menthyltin ( 9 ) hydrides as well as that of their organotin precursors are described. Whereas the reduction of acetophenone with 4 afforded (−)-(S)-1-phenylethanol in 40% ee, the reduction of the same ketone with dimethyl(−)menthyltin hydride yielded the alcohol with only a 7% ee. Full 1 H, 13 C, and 119 Sn NMR data are given.

Transmetallations between aryltrialkyltins and borane: synthesis of arylboronic acids and organotin hydrides

Abstract Aryltrialkyltin compounds react with borane in THF to give mixtures of trialkyltin hydrides and arylboranes, which on hydrolysis give arylboronic acid in high yields. The arylboronic acids are easily separated and obtained free of organotins.

Organotin hydride additions to E- And Z-trisubstituted ethylenes synthesis of some new functionally substituted organotin compounds

Abstract The syntheses of some new functionally substituted organotin compounds are reported. The results indicate that the additions of tri-n-butyltin and tri-phenyltin hydrides to trisubstituted ethylenes (where one substituent is either a carbomethoxy or a nitrile group) proceed smoothly to give high yields of organotin adducts and that the reactions are stereoselective. Evidence concerning the reversibility of the free radical forming step is presented.

Stereoselective hydrostannation of substituted alkynes with trineophyltin hydride

Hydrostannation of mono- and disubstituted alkynes with trineophyltin hydride (1) leads to vinylstannanes in good to excellent yields, the configuration of the products depending on the reaction conditions. Thus, whereas hydrostannation under radical conditions leads stereoselectively to only one of the two possible products corresponding to an anti addition in 60–99% yield, the additions catalyzed by bis(triphenylphosphine)palladium dichloride gave mixtures of the syn adducts (60–79% yield). Full 1H-, 13C-, and 119Sn-NMR as well as mass spectra data of the organotin adducts are given.

Chemo- and stereoselective reduction of (pivaloyloxy)methyl 6,6-dihalopenicillanates by trineophyltin hydride: Selective synthesis of 6β-halopenicillanates

Abstract A new Triorganotin hydride, Trineophyltin hydride was prepared and its chemo- and stereoselectivity towards reduction of Pom 6,6-homo- and hetero- dihalopenicillanates was examined. The trineophyltin hydride reveals higher stereoselectivity compared to that by tributyltin hydride at 25°C.

The reactions of diborane with aryl-organotin compounds

Abstract A number of tetraaryltin compounds, Ar 4 Sn (where Ar = phenyl, o - and p -tolyl, and p -chlorophenyl) and triphenyltin compounds, Ph 3 SnX (where X = Cl, H, OH, OCOCH 3 , and OCOCF 3 ) have been treated with diborane in tetrahydrofuran. Transmetallation occurs in which one or more aryl groups are transferred to boron. The organoboron intermediates give phenols upon oxidation and boronic and borinic acids upon hydrolysis. Pyridine complexes of organoboranes have also been isolated.

Synthesis and some properties of mixed alkyldi-(–)-menthyltin hydrides

The synthesis and physical properties of methyldi-(–)-menthyltin 4 and neophyldi-(–)-menthyltin 7 hydrides as well as those of their organotin precursors are described. The reaction of hydrides 4 and 7 with carbon tetrachloride shows that the reactivity of 4 is within the range of the more common triorganotin hydrides while the organotin hydride 7 reacts more slowly. A study of the reduction of acetophenone with both hydrides shows that whereas the reduction with 4 leads to (–)-(S)-1-phenylethanol (8.8% optical purity), the reduction with 7 affords (+)-(R)-1-phenylethanol (6.6% optical purity); these results indicate that some degree of asymmetric induction can be achieved. Full 1H, 13C and 119Sn NMR data are given.

Synthesis of asymmetrical aryl-tin compounds by cleavage of alkyl-tin bonds with sodium metal in liquid ammonia followed by SRN1 reactions with chloroarenes

Abstract One methyl-tin bond was selectively cleaved from aryltrimethyltin compounds by sodium metal in liquid ammonia. The triorganyl-stannyl anions thus obtained are arylated by chloroarenes by means of photostimulated S RN 1 reactions. Such reactions can be repeated to replace all methyl groups by different aryl groups. The one-pot synthesis of asymmetric triarylmethyltin compounds can be achieved from trimethyltin chloride.

Preparation and some reactions of neophyltin anions

Abstract A study on the preparation of trineophyltin and mixed methylneophyltin anions and subsequent reactions of these anions is reported. It was found that whereas mixed hydrides Me n Nph 3− n SnH ( n = 1,2) react with NaH in DMSO to give the corresponding organotin sodium anions (60–70% yield), trineophyltin hydride reacts with NaH to give hexaneophylditin as the only product (32%). The reaction of tin halides Me n Nph 3− n X (X = Cl, Br; n = 0, 1, 2) with lithium in THF yields the corresponding organotinlithium anions (70%). The tin anions were reacted with various alkyl halides. The 1,4 addition of trineophyltinlithium ( 10 ∗ ) to α,β-unsaturated enones followed by the reaction of the intermediate carbanions with methyl iodide, leads with benzylideneacetone to a mixture of the corresponding threo (34%) and erythro (25%) diastereoisomers. Under the same reaction conditions, the addition of 10 ∗ to chalcone proceeded with complete stereoselectivity to give the diastereoisomer threo (60%) as the only product. Full 1 H and 13 C NMR data of the new organotins are given.

Organotin compounds: X. Organotin hydride addition to methyl cyclohexene-1-carboxylate and methyl indene-3-carboxylate

Abstract Free radical hydrostannation of methyl cyclohexene-1-carboxylate (I) and methyl indene-3-carboxylate (III) with trialkyltin hydrides, R 3 SnH (R  Me, n-Bu, Ph) gives the energetically unfavourable cis products, 2-trialkylstannyl cyclohexanecarboxylate (II) and 2-trialkylstannyl indane-1-carboxylate (IV) in high yields, via a trans addition of the tin hydrides. The hydride abstractions by the intermediate trialkylstannylcyclohexanyl (VIII) and trialkylstannylindanyl (IX) intermediate radicals take place stereospecifically, and exclusively from the less hindered ring side. The structures of the isomers II and IV were established by (a) their transformation into the corresponding chlorodialkylstannyl derivatives V and VI, which were shown spectroscopically to have cis stereochemistries by intramolecular complexation of the ester group, and (b) their NMR data. Full 1 H, 13 C, and 119 Sn NMR data are given.