SULFUR- AND N-ACYL CARBONYL OXYGEN-ASSISTED HETEROLYSIS OF THE C(=O)–S BOND IN EXCITED-STATE (Z)-N-ACYL-α-DEHYDRO(1-NAPHTHYL)ALANINE THIOESTERS
摘要:
Irradiation of the title thioesters (Z)-1 in nitrogen-saturated 1,2-dichloroethane at wavelengths greater, than 280 nm was found to afford (Z)-4-(1-naphthylmethylene)-5(4H)-oxazolone derivatives (Z)-2, (E)-2, alkyl-substituted thiols 3, and (E)-1 without forming any thio-radical-derived products. An analysis of the substituent and solvent effects on the reactivity of 1 and the product distribution demonstrated that the heterolytic C(=O)-S bond cleavage products 2 and 3 are not derived from the long-lived acylium and thiolate ions but from the protonated oxazolone/thiolate ion pair. The latter intermediates were assumed to be formed by the sulfur-assisted nucleophilic addition of the N-acyl carbonyl oxygen to the thioester carbonyl carbon in the excited state, followed by the elimination of the thiolate ion from the resulting adducts.
Ligand‐Controlled Regiodivergent Thiocarbonylation of Alkynes toward Linear and Branched α,β‐Unsaturated Thioesters
作者:Han‐Jun Ai、Wangyang Lu、Xiao‐Feng Wu
DOI:10.1002/anie.202106079
日期:2021.7.26
the synthesis of unsaturated thioesters. A robust ligand-controlled regioselective thiocarbonylation of alkynes is developed. Utilizing boronic acid and 5-chlorosalicylic acid as the acid additive to in situ form 5-chloroborosalicylic acid (5-Cl-BSA), and bis(2-diphenylphosphinophenyl)ether (DPEphos) as the ligand, linear α,β-unsaturated thioesters were produced in a straightforward manner. Switching
A highly regioselective hydrocarbonylation of phenylacetylene with thiols and alcohols was developed using metal carbonyls/diazabicyclo[2.2.2]octane (DABCO) system at 100 °C in DMF. The use of Mo(CO)6 and thiols in the presence of DABCO was applied as an efficient Pd-free method for hydrothiocarbonylation of phenylacetylene into trans-α,β-cinamyl thioesters in excellent yields (88–98%). Similar reaction