Chloromethylene chloride

Butyrolactones are prepared by intramolecular reaction of haloallylic 2-alkynoates. The a-chloromethylenebutyrolactone 301 is prepared by the intramolecular reaction of300[150,151]. 4 -Hydroxy-2 -alkenyl 2-alkynoates can be used instead of haloallylic 2-alkynoates, and in this reaction, Pd(II) is regenerated by elimination of the hydroxy group[152]. As a related reaction, the q-(chloromethylene)-7-butyrolactone 304 is obtained from the cinnamyl 2-alkynoate 302 in the presence of LiCl and CuCbflSS]. Isohinokinin (305) has been synthesized by this reaction[l 54]. The reaction is explained by chloro-palladation of the triple bond, followed by intramolecular alkene insertion to generate the alkylpalladium chloride 303. Then PdCb is regenerated by attack of CuCb on the alkylpalladium bond as a key step in the catalytic reaction. 

Note The most common Vilsmeier reagent, (chloromethylene)dimethylammo-nium chloride (ClHC=+NMe2 CU), is usually made in situ from MesNCHO and POCI3, SOCI2, or COCI2. As well as chlorolysis of 0x0 substituents, these reagents are prone to react at other sites in the substrate molecule. 

Reaction of 55a with thionyl chloride gave the 3-chloromethylene compound (55b) (62%) and with isopropyl iodide the 3-isopropoxy-methylene derivative (55c) (57%). Hydroxylamine condenses with... 

Di Cesare and Gross175 introduced a procedure using phase-transfer catalysis to induce the action of dichlorocarbene on various protected sugars,176 and obtained the chloro derivative 162c from compound 161. Another, similar migration was observed,178 and confirmed,134,174 for the chlorination of methyl 2,3-anhydro-4,6-0-benzylidene-a-D-al-lopyranoside (166) with (chloromethylene)dimethyliminium chloride, which gave the rearranged chloro derivative 167. 

Treatment of the 9-formyl derivatives (241 R3 = H) with thionyl chloride gave 9-chloromethylene-4-oxo-6,7,8,9-tetrahydro-4//-pyrido [ 1,2-u] pyrimidines, which were then transformed with ammonium thiocyanate to the 9-thiocyanatomethylene derivatives.284... 

Chloromethylene)dimethylammonium chloride has been used to convert selected alcohols into sulfides in moderate to high yields with inversion of configuration.143... 

B. Cetinkaya, M. F. Lappert, G. M. McLaughlin, and K. Turner, Chloromethylene-ammonium Chlorides. Electron-Rich Carbenoids as Precursors to Secondary Carbene Metal Complexes Crystal and Molecular Structure of Trichloro(dimethylamino-methylene)bis(triethylphosphine)rhodium(III), J. Chem. Soc., Dalton Tram. 1974, 1591-1599. 

Dioxanes have been synthesized from l-O-allyl-l,2-diols by radical addition of per-fluoroalkyl iodides and subsequent nucleophilic cyclization.561 With sodium hydride, elimination occurs from iodides such as 1.3 other bases also give unsatisfactory results, whereas N-bromosuccinimide seems to be the reagent of choice for the cyclization to 1,4-dioxane 14. Similar results arc obtained with dibromodimethylhydantoin.561 Dihydrobenzofurans are synthesized by cyclodehydration utilizing the Vilsmeier reagent (chloromethylene)dimethylam-monium chloride is most practical.562 Nucleophilic aromatic substitution reactions with catechol derivatives also give the six-membered heterocycles.563 564 1.4-Dioxan-2-ones arc pre-... 

Chloro-9-(/3-D-ribofuranosyl)purine has similarly been prepared from inosine (63JOC945) by chlorination of 6-thioinosine (63MI40903) or, perhaps most successfully, by reaction of 2, 3, 5 -tri-0-acetylinosine with (chloromethylene)dimethylammonium chloride when yields of 70% are produced (B-78MI40903, p. 611). The latter reagent is obtained from phosgene and DMF in chloroform solution . 

---