ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .41. THIOENOL ETHERS BY INSERTION OF ALKYNES INTO M = C BONDS OF THIOCARBENE COMPLEXES AND DISENGAGEMENT OF LIGANDS ON SILICA-GEL

Organic Syntheses via Transition Metal Complexes, 41 1. ‐ Thioenol Ethers by Insertion of Alkynes into M = C Bonds of Thiocarbene Complexes and Disengagement of Ligands on Silica Gel A first example of reactions between alkynes and thiocarbene complexes is described. Et2NCCCCH3 (2) adds to (alkylthio)phenylcarbene complexes LnMC(SR)C6H5 (1) [LnM = Cr(CO)5. W(WO)5; RCH2CHCH2, CH2C6H5, c‐C6H11, t‐C4H9, C6H5] with insertion of the CC into the MC bond to form stereoselectively [(E)‐β‐(alkylthio)alkenyl]aminocarbene complexes LnMC(NEt2) ‐ C(CH3)C(SR)C6H5 [(E)‐3a–g]. With tungsten, but not with chromium, small amounts of indanone derivatives 4–6 were also obtained. We describe a straightforward and efficient method for the disengagement of ligands from carbene chromium complexes 3 on silica gel. Metal residues remain attached to the solid phase, and products are isolated by elution. Depending on the reaction conditions, different thioenol ethers 7–9 were obtained. Thus (E)‐3a–d on silica gel at ambient temperature under the influence of air give β‐(alkylthio)propenamides OC(NEt2)‐C(CH3)C(SR)C6H5 [(E)‐] and β‐(alkylthio)propenals OCH–C(CH3) = C(SR)C6H5 [(E)‐8]. Thermolysis of 3 on silica gel in the absence of oxygen leads to the formation of aldehydes 8 and 3‐(alkylthio)‐1‐indanones 5. Thermolysis of 3 on silca gel in the presence of sulfur yields β‐(alkylthio)propenethioamides 9 as the only products. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim