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Abstract: This paper reports results obtained in a study on the palladium-catalyzed hydrostannation of substituted propargyl alcohols with the bulky trineophyltin hydride (1). The reaction of 1 with 10 propargyl alcohols containing one up to three substituents, was carried out in THF at room temperature leading to the corresponding allylstannanes following in all cases a syn addition stereochemistry. These additions took place in good to excellent yields and, mostly, with a high degree of stereoselectivity. The results obtained suggest that the observed α/β regioselectivity might be ascribed to the steric bulk of the proximal substituents rather than to electronic effects. Full 1H-, 13C-, and 119Sn NMR characteristics are included. [Copyright &y& Elsevier]

Abstract: This paper reports the synthesis of dineophyltin dihydride (3) following two procedures. The four steps synthesis starting from benzyl chloride and Sn was shown to be more convenient than the two step direct alkylation of SnCl4. The study of the free radical hydrostannation of mono- and disubstituted acetylenes with hydride 3 shows that they are stereoselective and that the stereoisomers obtained in higher proportion are stable and easily separated by column chromatography. Some preliminary studies on the chemical reactivity of the new divinylsubstituted dineophyltin compounds in Stille reactions are also informed. Radical hydrostannatation of (E)-trisubstituted ethylenes with 3 did not succeed probably due to steric factors. The preparation of dineophyltin bromohydride (27) is also reported. Radical addition of 27 to methyl (E)-2,3-disubstituted propenoates leads to mixtures of the corresponding erythro and threo adducts in diastereomeric excesses (d.e.) in the range of 74–90%. [Copyright &y& Elsevier]

Abstract: This paper reports the results obtained in a study on the radical hydrostannation of mono- and disubstituted alkynes with bulky triorganotin hydrides using triethylborane as initiator. The addition of trineophyl- (1), tris[(phenyldimethylsilyl)methyl]- (2), and 9-tripticyldimethyltin (3) hydride to eight alkynes was carried out at room temperature leading to vinylstannanes in good to excellent yields and, mostly, with complete stereoselectivity. The results obtained in a study on the relative reactivity of trineophyl- (1), tris[(phenyldimethylsilyl)methyl]- (2), 9-triptycyldimethyltin (3) hydrides, and tri-n-butyltin hydride (29) using the radical reactions between these hydrides and 6-bromo-1-hexene (28) are also reported. Full 1H-, 13C-, and 119Sn NMR characteristics are included. [Copyright &y& Elsevier]

A study on the addition of trineophyltin hydride (1) to alkynones under free radical (AIBN and Et[sub 3]B) and palladium-catalyzed [(PPh[sub 3])[sub 2]PdCl[sub 2]] conditions is reported. The results obtained indicate that the addition of I to eight ynones catalyzed by bis(triphenylphosphine)palladium(II) chloride led in all cases to addition products in very high yields (80-96%). These additions take place with excellent regio- and stereochemistry, leading to the α adducts as major products in seven out of the eight cases studied. Also the E adducts, resulting from a syn attack, were the only (seven cases) or the predominant (one case) products. The radical hydrostannations initiated by AIBN of ynones 2-5 with 1 led to addition products in good yields (60-88%); with the more hindered ketones 6 and 7-9 the yields obtained were lower. The radical additions initiated by triethylboron to ynones 2-6 follow a similar pattern but with lower yields; no addition products in the hydrostannation of ynones 7-9 were detected. The new acyl-substituted vinylstannanes, owing to their greater stability compared with that of their tributyl- and trimethylstannyl analogues, can be purified by column chromatography using neutral alumina (in all cases) or silica gel 60 (in most cases) as adsorbents. Full ¹H, [sup 13]C, and [sup 119]Sn NMR data are given. [ABSTRACT FROM AUTHOR]