Corey-Winter alkene synthesis

COREY - WINTER Alkene synthesis Alkene synthesis from glycols via cyclic t, 2-lhionocartx)nates... 

The preparation of 4-alkenyl (3-lactams (II, Fig. 9) has been reported through either Homer-type olefination of a common 4-formyl (3-lactam or the Corey-Winter alkene synthesis applied to 4-dihydroxyalkyl (3-lactams [263]. 

Horton, D., Tindall, C. G., Jr. Synthesis and reactions of unsaturated sugars. XI. Evidence for a carbenoid intermediate in the Corey-Winter alkene synthesis. J. Org. Chem. 1970, 35, 3558-3559. 

Modified Corey-Winter Alkene Synthesis. Daub et al. have obtained satisfactory yields by using Fe(CO)s in an iron-mediated version (eq 36) of the reaction of thionocarbonates with Trimethyl Phosphite, which gives poor yields in the case of thermally labile alkenes. 

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. ... 

Corey-Winter olefin synthesis (I. I23.3-I234). Chong and Wiseman were able to demonstrate the transient existence of bicyclo[3.2.l]octenc-l (2, a bridgehead alkene which violates Bredt s rule) by application of the Corey-Winter olefin synthesis. Thus treatment of the thionocarbonatc (I) with triethyl phosphite at reflux (165°) fur 24 hr. in the presence of I,3-diphenyli obenzofurane (1, 342-343 2, 178-179) leads to the formation of two Diels-Alder adducts (3) and (4) derived from (2). 

Alkenes from 1,2-diols (7, 385-386). An efficient synthesis of (S)-(—)-y-methoxymethyl-a, /J-butenolide (3) from (+)-5-0-methyl-D-ribonolactone (1) involves conversion to the cyclic orthoformate 2 followed by pyrolysis to give 3 in 66.5% overall yield.1 In this case, the Corey-Winter reaction and the Hanessian route (8,192) were... 

The Corey-Winter reaction is a valuable route for the synthesis of unsaturated sugars and complex cycloalkenes. Alkenes may also be obtained by pyrolysis of methyl xanthates... 

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

The Corey-Winter reaction proceeds with complete stereospecificity by a syn elimination pathway, allowing the stereospecific synthesis of alkenes. Thus, anti-1,2-diphenylethane-1,2-diol was converted into cis -stilbene (2.45), whereas the corresponding syn-diol gave irans -stilbene. The strained fi-cyclooctene was prepared from the Z-isomer using this procedure (2.46). An alternative stereospecific route to alkenes proceeds from the diol with ethyl orthoformate or WA(-dimethylformanude dimethyl acetal, or by conversion of the diol to a 2-phenyl-1,3-dioxolane and treatment with an organolithium reagent to promote proton abstraction at C-2 and... 

Interestingly, both researches employed the same technique to install the methyl tetronate ring, that is, addition of the lithium anion of 4-methoxy-3-methyl-2(5H)-furanone to an aldehyde (106 or 113), but Kende used a TfjO-mediated dehydration to finish the synthesis, whereas Overman obtained the final structures after a Corey-Winter reaction to form the dialkoxy alkene unit (Scheme 1.16). In 2012, Martin et al. [77] managed to prepare enantioselectively Overman s intermediate 113 by an elegant cascade of reactions that culminates in the intramolecular dipolar cycloaddition of 119, prepared from 2-deoxy-D-ribose (120) (Scheme 1.16). 

The Corey-Winter synthesis has proved useful for the generation of a large number of structurally interesting alkenes, including some unstable alkenes that must be captured in situ (eq 2). ... 

---