Facile 1,1-Carboboration Reactions of Acetylenic Thioethers

Abstract

The acetylenic thioether PhSCCSPh undergoes a rapid 1,1-carboboration reaction with facile −SPh migration upon treatment with B(C 6 F 5 ) 3 to yield the borylated ketene dithioacetal product (PhS) 2 CC(C 6 F 5 )B(C 6 F 5 ) 2 (8a). The X-ray crystal structure analysis revealed an intramolecular sulfur−boron contact. The thioether PhCCSPh undergoes an analogous 1,1-carboboration reaction with B(C 6 F 5 ) 3 . The resulting vicinal S/B frustrated Lewis pair undergoes 1,2addition reactions to terminal acetylenes to give the respective zwitterionic six-membered heterocyclic sulfonium/borate products (all three examples were characterized by X-ray diffraction).

Fluorovinyl Thioethers as Putative Steric and Electronic Thioester Enolate Mimetics: Chemoselective HF Addition to Acetylene Thioethers

“…Also, the corresponding difluoride 2a was prepared in 48 % yield using 70 % HFpyridine. Phenylthioacetylene [21] 4b (prepared from phenylthioethynyl trimethylsilane 5) proved to be a particularly reactive substrate under our reaction conditions; the reaction was complete in 10 min, and furnished a 70 : 30 mixture of both the mono-and di-fluorinated compounds 1b and 2b. Lowering the temperature and increasing the amount of pyridine did not change the outcome -in fact at less than 50 % HF in pyridine, the reaction did not progress to completion, furnishing both 1b and 2b but in a lower conversion.…”

1,1-Carboboration to tellurium–boron intramolecular frustrated Lewis pairs

“…The use of B(C 6 F 5 ) 3 has helped to extend the scope of this type of reactions to include phos-phorus-substituted acetylenes 14,15 and unactivated acetylenes. 25 The facile carboboration of acetylenic thioethers using B(C 6 F 5 ) 3 gave a series of products that also served as S/B frustrated Lewis pairs (FLP). 24 Despite the variety of alkynes that have been subjected to 1,1-carboboration reactions, group 16-substituted alkynes in this context has only been reported recently.…”

“…[16][17][18] 1,1-Carboboration has also led to the facile synthesis of a variety of heterocycles and aromatic compounds, 19 including boroles, 20,21 stannoles, 22 1,4-stannaboracyclohexa-2,5-dienes 23 and 1-silacyclopent-2-ene. [25][26][27][28] While a previous report has described a single synthesis of a borylated vinyl telluroethers, 29 we now report the use of 1,1-carboboration to access a series of such species. 25 The facile carboboration of acetylenic thioethers using B(C 6 F 5 ) 3 gave a series of products that also served as S/B frustrated Lewis pairs (FLP).…”

Thiophene synthesis via 1,1-carboboration

“…10,11 In this manuscript, we describe an extension of this 1,1-carboboration protocol to the preparation of a series of thiophenes. 11 Suitably substituted linked thiophenes play an important role in organic materials chemistry. 12 Treatment of bis(phenylethynyl)sulfide 6a 13 with 0.5 molar equiv.…”