Thionolactones synthesis

Addition to thionolactones cyclic ethers. A wide variety of alkyliithium reagents add to the C=S group of thionolactones. The adducts, after reaction with CH,I, can be isolated in high yield as mixed methyl thioketals. The methylthio group can be removed by reduction with triphenyltin hydride (AIBN) to give cyclic ethers. The reaction is not dependent on the ring size and can be stereoselective, as shown by the synthesis of the ether lauthisan (2) from a thionolactone (1). 

Cyclization can also occur, as in the reported synthesis of thionolactones [234],... 

A recent synthesis of ( )-supinidine involved the same reaction as a key step to form a 5-membered ring [168]. An intermolecular reaction of a car-benoid with a thionolactone in the manno-series led to a thiirane and the alkene product of desulfurisation [67]. A similar process was observed in the case of a dithioester leading, after desulfurisation, to a thiophene, and a reaction with a thioamide furnished a thiocarbonyl ylid which could be trapped by an electron poor olefin [169]. 

Monothioacetals 1,3-Oxathiolanes Thiolactams S extrusion, 59-60, 261 Thiols synthesis from haloalkanes, 169, 269 Thionation of lactones, 110-111 Thiones olefination of, 35 Thionocarbonates. See Carbonothioates Thionolactones, 110-111 Thionyl chloride prepn. of acyl halides, 143 prepn. of carboxylic esters, 347 prepn. of haloalkanes from alcohols, 32 Thiophenoi. See Benzenethiol Thiotosylatc. See Benzenesulfonothioic add... 

Macrocyclic bis-thionolactones have been prepared with LR. These were converted by reduction with sodium naphthalenide into the radical anions, which gave bicyclic systems through radical dimerization and subsequent methylation (eq 14). This method was successfully applied by Nicolaou et al. in the total synthesis of hemibrevetoxin B. One of the crucial steps of the synthesis was the preparation of the bis-thiono ester (11), which was achieved by using LR together with tetramethylthiourea in xylene at 175 °CP... 

Thionation of Carboxylate Esters and Lactones. The reaction of esters and lactones with LR represents a well-established method for the synthesis of the corresponding thiocarbony 1 deriva-tives. - In fact, LR is the much superior reagent for the thionation of esters as compared with phosphorus pentasullide. Open-chain thionoesters have been conveniently obtained. Interestingly, natural triglycerides also smoothly react with LR to yield pure tristhionotriglycerides. Even better results are obtained with carboxylate esters if the improved solubilized LR or microwave irradiation are applied. The method has particularly been used for the preparation of cyclic thionoesters. Obviously there are very few structural or other restrictions that inhibit the formation of y-,S-, or macrocyclic thionolactones. Once more, microwave irradiation significantly improves the re-... 

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