Studies in group IV organometallic chemistry XXVII. Isomerization of the primary trans-addition products formed in the hydrostannation of ethynes

Abstract

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Hydrostannylation of Propargylic Alcohols Using Mixed Tin Hydrides

“…[20] By carefully choosing the reaction conditions the reaction can with very few exceptions be halted at the stage of the anti-addition product.…”

Stereoselective hydrostannation of substituted alkynes initiated by triethylborane and reactivity of bulky triorganotin hydrides

“…On the other hand, the formation of the Zvinylstannanes has been explained by considering that in the equilibrium mixture of the conformers corresponding to the intermediate alkyl radicals -the products of the addition of a second organotin radical -the conformers that Table 2 13 C NMR data of vinyltin adducts 5,10,15,16,20,22,24,26 lead via anti-elimination of the organotin radical to the Z-vinylstannanes are present in higher concentration. This has been ascribed to the favorable interaction between the tin atom and the neighbouring groups that predominates over the opposing effect of greater steric hindrance [5]. These results clearly demonstrate that, contrary to what has previously been stated [4,6,7], it is possible to carry out stereoselective radical hydrostannations of alkynes using organotin hydrides.…”

“…The formation of the E-adducts 4 and 25, entries 1 and 22, could be explained by taking into account that the known isomerization of the initially formed kinetic Z-products by further addition/elimination of the stannyl radical would lead to the thermodynamically more stable E-vinylstannanes [4,5]. On the other hand, the formation of the Zvinylstannanes has been explained by considering that in the equilibrium mixture of the conformers corresponding to the intermediate alkyl radicals -the products of the addition of a second organotin radical -the conformers that Table 2 13 C NMR data of vinyltin adducts 5,10,15,16,20,22,24,26 lead via anti-elimination of the organotin radical to the Z-vinylstannanes are present in higher concentration.…”

Synthesis of dineophyltin dihydride and stereoselective hydrostannation of alkynes and (E)-trisubstituted alkenes

“…In order to test the possibility of carrying out stereoselective hydrostannations, we studied the addition of hydride 3 under free radical conditions: nitrogen atmosphere, 0.01 equivalents of azobisisobutyronitrile (AIBN), without solvent at 80 C, to a series of four terminal alkynes: phenylethyne (7), 2-ethynylnaphthalene (8), propargyl alcohol (9), methyl propiolate (10), and of two internal alkynes: diphenylacetylene (11) and methyl 3-phenylpropiolate (12). The obtained results are summarized in Table 2.…”