Alkenyl phosphate

Table 26. Reaction between PerfIuoro-1-alkenyl Phosphates RfCF2CF=CR0P(0)(0C2Hs)2 and Phosphonium YUdes Ph3P=CR R To Give RfCF=CFCR=CR R [79]...

Polyfluoro-l -alkenyl phosphates are reduced under mild conditions by diisobuty-laluminum hydride (DIBAL) to the aluminum enolate, which is denvatized by addition to benzaldehyde [96] (equation 78)... 

Figure 13.25 presented the stereoselective synthesis of ester-substituted, E- or Z-config-ured alkenyl phosphates.. 

In place of the aryl halide or alkenyl halide, the corresponding phosphate or triflate have been employed for the above cross-coupling reaction (O Scheme 71) [102]. These substrates were easily prepared from the corresponding lactone. The reaction of alkenyl phosphate or triflate has frequently been employed in the synthesis of marine polycyclic ethers such as brevetoxin... 

Kuroboshi, M. Shinozaki, T. Ishihara, T. Ando, T. A convenient synthesis of fluorine-containing highly-substituted furans through new fluoride ion-catalyzed reaction of l-alkyl-F-l-alkenyl phosphates. Chem. Lett. 1987, 1621-1622. 

The cleavage of carbon-oxygen bonds from alkenyl or aryl phosphates can be accomplished under reductive conditions with a low valent metal. As vinyl phosphates can be formed readily from ketones, this procedure provides a method to convert a ketone to an alkene. For example, the alkenyl phosphate 74 was prepared by trapping the enolate formed on reduction of the enone 73 and was converted into the alkene 75 (7.55). The chemistry therefore provides a method to prepare structurally specihc alkenes. Low-valent titanium (prepared for example by reduction of titanium(III) chloride with potassium metal) is a convenient alternative to lithium or sodium in liquid ammonia or an amine for the reductive cleavage of alkenyl or aryl phosphates. 

Palladium-catalyzed aminocarbonylations of alkenyl phosphates have been investigated using Mo(CO)6 as a solid carbon monoxide source. The reactions afforded a wide variety of acrylamides (78) after 20 min of microwave irradiation in moderate to good yields (Scheme 16). ... 

It may be of interest that other sp electrophiles such as alkenyl phosphates [60], heteroaryl thioethers [61], and aryltrimethylammonium triflates [62] have recently been added to the portfolio of substrates for palladium-catalyzed coupling reactions. 

Alkenyl phosphates, prepared from the corresponding ketones, as well as alkenyl halides undergo nickel-catalyzed cross-coupling reactions to yield aUylsilanes (eq 18). The reactions are stereospecific. 

In addition, other electrophiles, such as arylsulfonyl hydrazides, aryl sulfamates, aryl sulfinates, or alkenyl phosphates, have been reported to arylate heterocycles, such as benzoxazoles or xanthines. 

Having established conditions for the Heck reaction employing alkenyl phosphates as electrophiles obtaining the non-migrated products, further exploration of... 

During the studies on the implementation of alkenyl phosphates in the palladium catalyzed Negishi reaction producing 1,1-disubtituted alkenes, a new effective palladium 1,2-migration was discovered (Scheme 3.1)[2]. 

Initial investigations were performed using the alkenyl 0,0-diphenyl phosphates adaptable in the Heck reaction. However, substantial amounts of unwanted byproducts such as homocoupling of the alkenyl phosphate were obtained, when these electrophiles were employed, and cleaner reactions were observed, when the corresponding 0,0-diethyl phosphates and tosylates were introduced. 

Next, attention was directed towards the nucleophilic nature of the organozinc reagent potentially affecting the 1,2-migration. Various alkenyl phosphates and tosylates were coupled to arylzinc chlorides possessing different electronic and sterical properties. All reactions were conducted using the optimized catalytic... 

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