Reaction with alkenyl sulfides

Failure to achieve the bicyclization of diallyl ether with nBu2ZrCp2 led to the unexpected discovery of the oxidative addition reaction,226 shown in Scheme 44. This reaction has been extensively used for developing synthetically useful reactions, also shown in Scheme 44 232 234>234a-234c Another breakthrough on this topic was made with alkenyl chloride,235 which led to more recent similar discoveries with alkenyl sulfides, sulfones, and ethers236,23611 237 (Scheme 45). 

AIkylthio)allylritanium reagentS, RSCH=CHCH2TiL (l).9 The reagents are prepared by deprotonation of allylic alkyl (aryl) sulfides with sec- or r-butyllithium followed by addition of Ti(0-/-Pr)4 at - 78°. They can react with carbonyl compounds at the a- or "/-position. a-Adducts predominate in reactions with a- and /1-mono- and disubstituted sulfides, whereas /-adducts predominate in reaction with /-substituted sulfides. The a-adducts show high eryr/iro-selectivity. The products are useful precursors to alkenyl oxiranes and to 2-(arylthio)-l,3-butadienes. 

Aryl and alkenyl phenyl sulfides are prepared by the reaction of aryl and alkenyl halides and inflates with tributylstannyl phenyl sulfide. 2-Chloropyrimidine (737) is used for the coupling[606,607]. The diaryl or divinyl sulfide 739 is prepared by the reaction of distannyl sulfide (738)[548], N,N-Diethylaminotributyltin (740) reacts with aryl halides to give arylamines[608]. 

Aryl sulfides are prepared by the reaction of aryl halides with thiols and thiophenol in DMSO[675,676] or by the use of phase-transfer catalysis[677]. The alkenyl sulfide 803 is obtained by the reaction of lithium phenyl sulfide (802) with an alkenyl bromide[678]. 

The Lewis acid catalyst 53 is now referred to as the Narasaka catalyst. This catalyst can be generated in situ from the reaction of dichlorodiisopropoxy-titanium and a diol chiral ligand derived from tartaric acid. This compound can also catalyze [2+2] cycloaddition reactions with high enantioselectivity. For example, as depicted in Scheme 5-20, in the reaction of alkenes bearing al-kylthio groups (ketene dithioacetals, alkenyl sulfides, and alkynyl sulfides) with electron-deficient olefins, the corresponding cyclobutane or methylenecyclobu-tene derivatives can be obtained in high enantiomeric excess.18... 

The rhodium-catalyzed hydroboration has opened the way to cyclization reactions starting from dienes [92], For instance, rhodium-catalyzed hydroboration of the terminal alkenyl group of an os/Tunsaturated lactone followed by reaction with the PTOC-OMe chain transfer reagent afforded the bicyclic a-S-pyridyl lactone in 63% yield (Scheme 39). After oxidation of the sulfide with m-CPBA, thermal elimination of the sulfoxide afforded the corresponding a-methylene lactone in 65% yield. Interestingly, such bicyclic a-methylenelactones are substructures that can be found in many natural products such as mirabolide [93]. 

Reaction of the alkenylmagnesium intermediates 184 with several electrophiles led to trisubstituted alkenyl sulfides 186 (Table 14). Thus, when the reaction was quenched with D2O, the deuteriated vinyl sulfide (186 E = D) was obtained in 80% yield with 98% deuterium incorporation. The reaction with aldehydes, benzoyl chloride and iodine gave moderate to good yields of the desired functionalized alkenyl sulfides (186) however, ethyl chloroformate did not give good result. 

The treatment of 7V-tosyl-/>-anisidine (75) and several of its derivatives with BTIB in the presence of activated alkenes provides an interesting example of an intermolecular cyclodehydrogenation sequence (99H1785). Arylpropenes are converted to 7V-tosylindolines 76 under these conditions, while alkenyl sulfides lead to the 7V-tosylindoles 77 (Scheme 22). The intermediate formation of 7V-tosylnitrenium ions in these reactions was suggested. 

Nucleophilic substitution of a,/3-epoxysilanes followed by the Peterson elimination is valuable for the stereoselective synthesis of alkenes.3 The reactions with lithium phenylsulfide and diphenylphosphide form alkenyl sulfides and alkenylphosphines, respectively, in a stereospecific manner. 7-Metallo-a,/ -epoxysilanes are isomerized to a-siloxyallylmetals by anionic ring opening and subsequent Brook rearrangement (Equation... 

Macrolides. Reaction of a-alkenyl cyclic sulfide (1) with dichloroketene is accompanied by a [3.3] sigmatropic rearrangement lo give the 10-membered thiolactone (2) (c/. 9, 153-154). After dechlorination and deprotection, reaction with camphorsulfonic acid (CSA) effects an S-to-O acyl transfer to give the mercapto lactone (3). 

Alkyl and allyl sulfides and selenides can be transformed readily into the corresponding alkyl and alkenyl halides respectively. This reaction takes advantage of the easy formation of the corresponding sul-fonium and selenonium salts on reaction with alkyl halides, alkyl bromoacetates or bromine - (Scheme S3). A related process involves the intermediary formation of a selenoxide and its further reaction with hydrochloric or hydrobromic acids. ... 

Allyiic halides, alcohols, ethers, acetates, lactones, phosphates, epoxides, sulfides, sulfonium salts, se-lenides and ammonium salts undergo transition metal catalyzed coupling reactions with C(sp )—Li, —Mg, —B, —Al, —Sn, —Zt, —Cd and — Hg reagents. Table 1 summarizes the allyiic leaving groups, alkenyl and aryl metallic reagents, catalytically active metals and references and Table 2 the regio- and stereo-chemical aspects. 

Alkenes. Titanocene bis(triethyl phosphite), which is prepared in situ from titanocene dichloride, triethylphosphite, and Mg, promotes carbonyl olefmation with gem-dichlorides and dithioacetals [e.g., l,l-bis(phenylthio)cyclobutane ] including those derived from enals (to give 1,3-dienes). Enol ethers-and alkenyl sulfides are obtained in the analogous reaction with dithioorthoformates and trithioorthoformates. Cross-coupling of dithioacetal and thiolesters furnishes predominantly (Z)-alkenyl sulfides. ... 

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