Reaction of silyl thioketones with lithium diethylphosphite: first observation of Thia–Brook rearrangement

Abstract

Reaction of silyl thioketone 7 with lithium diethylphosphite at-98 °C afforded an S-attack product 8 and a formal C-attack products 10 and 11, which were formed by S-to-C migration of the phosphoryl group in 8 followed by C-to-S migration of the silyl group (thia-Brook rearrangemnet), in a ratio depending on the conditions. The relative facility of the thia-Brook rearrangement was compared with that of the Brook rearrangement using the (t-butyldimethylsilyl)diphenylmethyl derivatives 22 and 23.

Synthesis of new organosilicon compounds by CS2: Mercapto-silyl-thiones

“…Although the precise mechanism of this reaction is not clear at the present time, it is reasonable to assume that the reaction path with attention to 1 H and 13 C NMR data [ 1 H NMR: 0.17 (s, 18H, SiMe 3 ), 3.14 (b.s, 1H, SH), 4.45 (s, 2H, CH 2 ), 7.28 (m, 5H, Ar); 13 C NMR: À1.13 (SiMe 3 ), 41.07 (CH 2 ), 54.94 (C(SiMe 3 ) 2 SH), 126.28e135.23 (Ar), 213.62 (C]S)] involves the initial attack of trisyl anion at the carbon of carbon disulfide followed by a silyl migration from carbon to sulphur (1b) (Thia-Brook rearrangement) [27,28] and the formation of carbanion 1b [29] and then conversion to the enethiolate 1c [16,30]. The resulting product (1) shows that the migration of sulphur to carbon of C(SiMe 3 ) 2 has been occurred.…”

Progress in the Chemistry of Phosphorothioates

“…Another method to generate the carbanion in a-position to the S-atom, consisted in the thiophilic attack of silyl thioketones with lithium diethylphosphite. [48] Then, the reaction proceeded in the phosphorothioate to mercaptophosphonate rearrangement followed by the migration of the silyl…”

Cesium carbonate-catalyzed synthesis of phosphorothioates via S-phosphination of thioketones

“…22 Takeda et al have developed a reaction between silyl thioketone and lithium diethyl phosphite at −98 °C to afford a thiophilic attacked product as a major product, whereas S -attacked and thia-Brook rearranged products were found as minor products (Scheme 1c). 23 However, these protocols showed some limitations and drawbacks such as limited substrate applicability, safety issues, and harsh reaction conditions required for the completion of the reactions. For the above-mentioned reasons, an environmentally friendly, atom-economical, and mild reaction condition protocol for the preparation of phosphorothioates is still desired in this field.…”