Alkenyl chlorides

Alkenyl chlorides are generally not very reactive, bnt vinyl chloride is exceptionally reactive and its carbonyiation with NH3 at 100 "C gave the Michael adduct of acrylamide 506 in high yields[360]. 

The rather unreactive chlorine of vinyl chloride can be displaced with nucleophiles by the catalytic action of PdCb. The conversion of vinyl chloride to vinyl acetate (797) has been studied extensively from an industrial standpoint[665 671]. DMF is a good solvent. 1,2-Diacetoxyethylene (798) is obtained from dichloroethylene[672]. The exchange reaction suffers steric hindrance. The alkenyl chloride 799 is displaced with an acetoxy group whereas 800 and 801 cannot be displaccd[673,674]. Similarly, exchange reactions of vinyl chloride with alcohols and amines have been carried out[668]. 

Simple alkyl and alkenyl ethers of pentaerythritol are produced on direct reaction of the polyol and the requited alkyl or alkenyl chloride in the presence of quaternary alkylamine bromide (44). AHyl chloride produces the pentaerythritol tetraHyl ether [1471 -18-7],... 

Tetrahalobenzynes, however, react with a variety of aromatic compounds to afford tetrahalobenzobarrelene derivatives in good yields, frequently in the range of 55 to 75%. The dehalogenation of a variety of alkenyl chlorides with alkali metals in tetrahydrofu-ran containing tert-butyl alcohol suggested this approach to the dechlorination of tetrachlorobenzobarrelenes. 

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). 

Symmetrical 2,2-disubstituted-l-lithio-l-chloroalkenes mono-insert cleanly into zirconacycles to give trisubstituted olefin products in high yield following protic work-up of the ring-expanded six-membered zirconacycle (Scheme 3.18 R1 = R2 = alkyl) [48]. The insertion of non-symmetrical 2,2-disubstituted alkenyl carbenoids has not yet been reported. A wide range of 2-monosubstituted alkenyl carbenoids (51, 52, 60, 62) arising from in situ deprotonation of alkenyl chlorides can be successfully inserted into zirconacyclopen-tanes and -pentenes with the expected inversion of configuration at the carbenoid carbon [49,50],... 

E-Alkenyl halides.1 Iodoform in combination with CrCl2 reacts with an aldehyde at 0° to form an (E)-alkenyl iodide in 75-90% yield. Replacement of CHI, by CHC13 and use of higher temperatures results in (E)-alkenyl chlorides. (E)-Alkenyl bromides can be obtained by use of CHBr3 and CrBr2. The E/Z ratio increases in the order I < Br < Cl, but the rate is in the order I > Br > Cl. Ketones undergo this reaction very slowly. 

Organobismuth compound 1" was also used for the cross-coupling reaction with alkenyl triflates. CC Et-substituted cyclopentenyl triflate afforded the coupling product quantitatively, while the sterically hindered triflate gave the product in poor yield (Scheme 39) [44], Azabismocine 2 reacted with activated alkenyl chlorides to give the coupling products in moderate to good yields (Scheme 40) [54],... 

Scheme 40 Cross-coupling reaction of phenylazabismocine with alkenyl chlorides...

Some of the notable recent developments in the Pd- or Ni-catalyzed aryl-alkenyl and alkenyl-aryl coupling reactions include the use of aryl and alkenyl chlorides along the lines of earlier discussions. lust a couple of representative examples of the aryl-alkenyl coupling reaction with alkenyl chlorides are shown in Scheme 33. 

SCHEME 67. Alkylation of alkenyl chlorides with alkylmagnesiums in the presence of Pd catalysts... 

SCHEME 68. Pd- or Ni-catalyzed alkylation of aryl and alkenyl chlorides with alkylzincs... 

Norbomadiene affords chiefly the alkenyl chloride, but significant amounts of nortricyclyl product are... 

Figure 16.2 The more common low-molecular-mass alkenyl chlorides...

The influence of an olefinic double bond in alkenyl chlorides pyrolyses66 has been assessed and described in Table 18. The vinyl substituent showed a significant rate-enhanc-... 

TABLE 19. Arrhenius parameters and comparative rates of alkenyl chlorides pyrolysis at 440 °C... 

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