Stereoselective hydrostannation of diacrylate and dimetacrylate esters of galactaric acid derivatives: cyclohydrostannation vs diaddition

This paper reports a study on the free radical hydrostannation of ((4S,4'R,5R,5'S)-2,2,2',2'-tetramethyl-[4,4'-bi(1,3-dioxolane)]-5,5'-diyl)bis(diphenyl methylene) diacrylate (1) and dimethacrylate (2) with triorganotin hydrides, R₃SnH (R = Me, n-Bu, Ph). The preliminary investigations show that these reactions could lead to mixtures of products of cyclohydrostannation and/or mono- or diaddition according to the organotin hydrides employed and the reaction conditions used. The addition of Me₃SnH to 1 afforded a mixture of three organotin compounds from which it was obtained pure the new 13-membered macrodiolide 3 (48%). The other two organotins could not be separated and they probably are products of mono or diaddition. The addition of n-Bu₃SnH to diester 1 led to a mixture of two organotins, the one in major proportion (91%) being the product of diaddition 4. The minor product (9%) could not be isolated pure. The hydrostannation of 1 with Ph₃SnH led to one organotin: the product of diaddition 5. The hydrostannation of the dimethacrylate 2 with the organotin hydrides R₃SnH (R = Me, n-Bu, Ph) under the same reaction conditions, led in the three cases to mixtures containing mainly diaddition products, and no cyclization products being detected. Some physical characteristics of the new compounds including selected values of ¹H, ¹³C, and ¹¹⁹Sn, NMR are included.