Thiono lactones

This is a valuable procedure because medium and large ring ethers are not easily made, while the corresponding thiono lactones can be prepared from the readily available lactones (see, e.g., 10-23) by Reaction 16-10. 

Ring expansion of thiono lactones (cyclic ethers)... 

Better results are obtained with ruthenium complexes of the corresponding thiono-lactones. Reductive ring cleavage with LiAlH4, then methylation and decomplexation, leads to the thioether (76 % ee). The chiral ruthenium complex recovered in this step can be converted back into the starting complex in two steps (Sch. 7) [55]. 

BC13 convert 0=0 groups of ketones, lactones, and lactams to G=S groups119 and H2S-Me3SiCl-i-Pr2NLi converts carboxylic esters to thiono esters.120 Carboxylic acids RCOOH can be converted directly to dithiocarboxylic esters RCSSR, 120a in moderate yield, with P4S, and a primary alcohol R OH.121 Thioketones can also be prepared by treatment of ketones with P4SI0,122 and from oximes or various types of hydrazone (overall conversion C=N------> C=S).123... 

PhjSnH-AIBN in toluene (10 examples, 72-99%). Accordingly, a two-step conversion of esters and lactones to ethers via thionoesters/lactones can be achieved on this basis. 2-Thiono-l,3-dioxolanes are similarly desulfurized to give the dioxolanes, therefore diols can be protected in the form of heterocycles which are acid-stable but eventually switched to acid-sensitive entities. 

Thiono esters and lactones are o HcB. Partial dechlorination of pi ly Rh-phosphine catalyst proceeds in h... 

Thiono esters and lactones are important intermediates in modern organic synthesis since they easily undergo useful follow-up reactions. Ethers are formed on reduction with Raney nickel or... 

Thiono Esters and Lactones. Although thiono esters can be conveniently prepared via imidates, the introduction of LR for the thionation of esters represents a great advance in synthetic methodology since ordinary esters are used as educts and P4S10 only reacts with esters if enforced reaction conditions are applied, under which many thiono esters decompose. Facile conversion of... 

The reaction is completed within 5-15 min if tetralin at 210 °C is used as solvent. Also, dithio-y-lactones, including dithio-phthalides and dithio-Q -p)Tones, are formed smoothly whereas the hitherto unknown simple or 3-dithiolactones cannot be prepared, neither with LR nor by any other method. Interestingly, dithiopilocarpine is formed as a mixture of diastereomers on reaction of pilocarpine with LR (eq 16), i.e. both oxygen atoms of (12) are replaced by sulfur. In an interesting sequence of thion-ation and rearrangement reactions, three different thiono analogs of 1,8-naphthalic anhydride were prepared (eq 17). ... 

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