Cyclic thionocarbonates, synthesis

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

Olefin synthesis. Corey and Winter" devised a novel olefin synthesis from 1,2-diols utilizing in the first step the reaction with thiocarbonyldiimidazole (2), a reagent prepared from 2 moles of imidazole and 1 mole of thiophosgene. Corey postulated that treatment of the cyclic thionocarbonate (3) with a reagent which would abstract sulfur to form the curbenc (4) would effect cis elimination to the olefin and found that trimethyl phosphite effects this reaction cleanly and in high yield. [Pg.1350]

The Corey-Winter olefin synthesis is a two-step transformation of a diol 1 to an olefin 3.1"3 A cyclic thionocarbonate 2 is prepared from the diol 1, and subsequent heating of 2 with phosphite affords olefin 3. 

In 1963, Corey and Winter disclosed their discovery of a new method for the stereospecific synthesis of olefins from 1,2-diols. Treatment of mejo-hydrobenzoin 4 with carbonyldiimidazole in toluene at reflux gave the corresponding cyclic thionocarbonate 5 with quantitative conversion. Exposure of 5 to trimethylphosphite then afforded cis-stilbene 6 in 92% yield. fraHJ-Stilbene could be obtained by starting with the corresponding tram-diol. This two-step reaction sequence could also be used for the synthesis of cyclic olefins. Treatment of rraiw-cyclodecanediol 7 with... 

The syn alcohol 657 contains the stereochemistry required for a synthesis of ( + )-660b. The 2,6-disubstituted piperidine 659 is prepared from 657 in seven steps. Conversion of 659 to the cyclic thionocarbonate followed by heating with trimethylphosphite produces the -olefin 660a which undergoes a Birch detosylation to afford ( + )-660b (Scheme 145). 

Full details on the synthesis of 5-thio-D-glucose based on the radical promoted rearrangement of cyclic thionocarbonate 38 to 5,6-S,0-thiolcarbonate 39 have... 

Ziegler EE, Metcalf III CA (1992) Confirmation by Total Synthesis of the Revised Structure of Sporol An Application of Cyclic Thionocarbonate-initiated Radical Cyclization. Tetrahedron Lett 33 3117... 

The many useful reactions of organophosphites include dehalogenation (12.294), desulphurisation (12.295), deoxygenation (12.296, 12.297), reductive cyclisation (12.298-12.300), reduction of peroxides to ethers (12.301), synthesis of quinolines (12.302) and cleavage of cyclic thionocarbonates (Corey-Winter reaction) (12.303) [15]. 

Synthesis of olefins from 1,2-diols and thiocarbonyldiimidazole. Treatment of the intermediate cyclic thionocarbonate with trimethylphosphite yields the olefin by cis-elimination ... 

Alkene Synthesis. The Corey-Winter alkene synthesis is an effective method for the deoxygenation of vicinal diols. The method involves formation of a l,3-dioxolane-2-thione [cyclic thionocarbonate (or thiocarbonate)] by treatment of a vicinal diol with TCDI. Decomposition of the thionocarbonate, usually with a phosphorus compound, affords the alkene (eq 1 ). The breakdown of the thionocarbonate occurs in a stereospecific sense details of investigations into the mechanism have been summarized. ... 

Alkene synthesis from glycols via cyclic 1,2-thionocarbonates (Corey-Winter) or 1,3-dioxolanes (Eastwood) (see 1st edition). 

COREY WINTER Alkenesynthesis Alkene synthesis from glycols via cyclic 1,2-thionocarbonates. 

Several examples of the applicability of carbon disulphide in the synthesis of cyclic as well as open-chain thiono- and trithio-carbonates have appeared. Thus dithallous glycolates reacted with excess of carbon disulphide to form ethylenethionocarbonates together with spiro-orthocarbonates, and the formation of tetramethyl orthocarbonate in the reaction between thallous ethoxide and carbon disulphide evidently proceeded via intermediate diethyl thionocarbonate. Klingsberg obtained 5,6-dimethyl-l,3-dithiole-2-thione by the reaction of 4,5-dimethylbenzene-1,2-dithiol with carbon disulphide. The thiirans (390 R = Me, R = R = H) reacted with carbon disulphide in basic media to yield 4-methylthio-l,3-di-thiole-2-thiones (429). Successive treatment of 2,2-diphenylethylene-sulphonamide with carbon disulphide and alkyl halides in the presence of a base afforded the unsaturated trithiocarbonate (430), and the symmetrical trithiocarbonate (431) was formed by the simultaneous action of sodium sulphide and carbon disulphide on the oxathiolan derivative (432). ... 

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