Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Alkenyl triflate

Vinyl acetate reacts with the alkenyl triflate 65 at the /3-carbon to give the 1-acetoxy-1,3-diene 66[68]. However, the reaction of vinyl acetate with 5-iodo-pyrimidine affords 5-vinylpyrimidine with elimination of the acetoxy group[69]. Also stilbene (67) was obtained by the reaction of an excess of vinyl acetate with iodobenzene when interlamellar montmorillonite ethylsilyl-diphenylphosphine (L) palladium chloride was used as an active catalyst[70]. Commonly used PdCl2(Ph3P)2 does not give stilbene. [Pg.138]

Scheme 7.2 Heck reactions of dihydrofuran with aryl or alkenyl triflates with R)-BITIANP. Scheme 7.2 Heck reactions of dihydrofuran with aryl or alkenyl triflates with R)-BITIANP.
The versatility of Pd-catalyzed coupling of stannanes has been extended by the demonstration that alkenyl triflates are also reactive.199... [Pg.733]

The alkenyl triflates can be prepared from ketones,200 and methods are available for regioselective preparation of alkenyl triflates from unsymmetrical ketones.201... [Pg.733]

This method can also be applied to alkenyl triflates. [Pg.752]

The multi-component procedure is also effective for the chromium-catalyzed addition of organic halides to aldehydes (the Nozaki-Hiyama-Kishi reaction) [73]. The active Cr(II) species is recycled by redox interaction with Mn powder as the stoichiometric co-reductant in the presence of MesSiCl (Scheme 34), which mainly liberates the chromium catalyst from the alkoxide adduct. The chemo- and diastereo-selective addition reaction is performed with a variety of organic halides and alkenyl triflates. In the case of crotyl bromide, the addition is highly stereoconvergent, i.e., the respective anti-... [Pg.81]

Another sequence involving an anionic and a Pd-catalyzed step was described by the groups of Rossi and Arcadi [477]. These authors prepared substituted tetrahy-dro-2H-pyrrolo[3,2-c]pyrazolones 2-934 starting from hydrazones 2-932 and aryl-halides or alkenyl triflates 2-933 (Scheme 2.208). The first step is the formation of a pyrazolone. There follows cleavage of the urea moiety with piperidine and an inter-as well as an intramolecular Heck-type reaction with 2-933. [Pg.191]

In addition, aryl triflates have proven to be viable substrates for the Pd-catalyzed Csp2—P bond formation reactions [87-90], Intriguingly, phosphorylation can be achieved from the Pd-catalyzed coupling of alkenyl triflate with not only dialkylphosphites, but also with hypophosphorous acid [88]. Thus, phosphinic acid 87 was obtained when triflate 86 was treated with hypophosphorus acid in the presence of Pd(Ph3P)4. Due to the abundance of alkenyl triflates and milder reaction conditions, alkenyl triflates have certain advantages over the corresponding alkenyl halides as substrates for Pd-catalyzed phosphorylations to make alkenyl phosphonates or phosphinates. [Pg.20]

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],... [Pg.218]

Scheme 39 Cross-coupling reaction of phenylbismuth alkoxide with alkenyl triflates... Scheme 39 Cross-coupling reaction of phenylbismuth alkoxide with alkenyl triflates...
Regio- and enantioselective Heck reactions of 2 3-dihydrofuran with aryl and alkenyl triflates in the presence of the chiral ligand (R)-BITIANP provides 2-substituted 23-dihydro-furans with complete regioselectivity, high enantioselectivity (86-96% ee) and good yields (76-93%) <99CC1811>. A catalytic oxyselenylation-deselenylation reaction of alkenes offers a stereoselective one-pot conversion of alkenes into 2 -dihydrofurans <99EF0797>. [Pg.149]

The addition of LiCl and Cul, and triphenylarsine as ligand are required to suppress side-reactions in the carbonylative cross-coupling of geminally substituted alkenyl triflate in the synthesis of sarcodictyin. Stereochemical configuration of the double bond of organotin compound was completely lost in this reaction (Equation (5)). " ... [Pg.413]

Vinyl triflates. Use of this hindered, non-nucleophilic base (1) allows direct conversion of aldehydes to vinyl triflates (equation 1). The method is also applicable to Conversion of ketones to 1-alkenyl triflates. [Pg.123]

In an oxidative addition, Pd(0) complex 22 with BINAP as a ligand accepts alkenyl triflate It. The resulting Pd complex 23 is cationic, since the triflate anion is bound only loosely to the palladium and dissociates from the complex.1 Syn insertion of one of the two enantiotopic double bonds of the cyclopentadienc into the alkenyl-Pd bond of complex 23 leads firs to q -allyl-Pd complex 24. This is in rapid equilibrium with t 3-allyl-Pd complex 25. Neither 24 nor 25 contains a p-H atom in a yn relationship to palladium. Moreover, internal rotation is impossible in the con form a-tionaily fixed ring system. For this reason there is no possibility of a subsequent p-hydride elimination that would once again release the palladium catalyst. In a normal Heck reaction (see discussion) the catalytic cycle would be broken at this point. [Pg.47]

Three types of reaction systems have been designed and applied for the enantioposition-selective asymmetric cross-coupling reactions so far. First example is asymmetric induction of planar chirality on chromium-arene complexes [7,8]. T vo chloro-suhstituents in a tricarhonyl("n6-o-dichlorobenzene)chromium are prochiral with respect to the planar chirality of the 7t-arene-metal moiety, thus an enantioposition-selective substitution at one of the two chloro substituents takes place to give a planar chiral monosubstitution product with a minor amount of the disubstitution product. A similar methodology of monosuhstitution can be applicable to the synthesis of axially chiral biaryl molecules from an achiral ditriflate in which the two tri-fluoromethanesulfonyloxy groups are enantiotopic [9-11]. The last example is intramolecular alkylation of alkenyl triflate with one of the enantiotopic alkylboranes, which leads to a chiral cyclic system [12], The structures of the three representative substrates are illustrated in Figure 8F.1. [Pg.654]

Asymmetric induction of central chirality at a carbon atom was achieved by an intramolecular enantioposition-selective asymmetric cross-coupling [12]. Treatment of the prochiral bisbo-rane 46, which was prepared from the alkenyl triflate 45 and 2 equiv. of 9-BBN with 20 mol % of Pd/(S)-(/ )-BPPFOAc (48) catalyst generated in situ in THF, brings about intramolecular Suzuki coupling. The following oxidative workup and p-nitrobcnzoylation affords the chiral cyclopentane derivative (R)-47 in 58% yield and 28% ee (Scheme 8F.14). [Pg.665]

Alkenyl triflates were established by Fiirstner s group as suitable substrates (Table 5.3) [17]. A variety of alkenyl triflates of ketones, P-keto esters and cyclic... [Pg.149]

TMS group is used for protection of terminal alkynes. However, alkynylsilanes themselves can be used for the coupling with aryl and alkenyl triflates using Pd-CuCl as a catalyst [74], Thus the internal alkyne 160 is prepared by stepwise reactions of two different triflates 157 and 159 with trimethylsilylacetylene (134) via 158. [Pg.49]

Primary alkylboranes derived by hydroboration of terminal alkenes with 9-BBN-H are coupled with aryl and alkenyl triflates and halides under properly selected conditions. The reaction proceeds smoothly without elimination of /1-hydrogen using PdCTklppf) or Pd(Ph3P)4 and K3PO4 in dioxane or DMF [132]. The intramolecular cross-coupling of the alkenyl triflate with the alkylborane in 292, prepared by in situ hydroboration of the double bond in 291 with 9-BBN-H, is applied to the annulation to... [Pg.66]

Optimum conditions for the coupling of the alkenyl triflates 330 with the arylstannanes 331 have been studied. Ligandless Pd complexes such as Pd(dba)2 are most active in the reaction of the enol triflate. PI13P inhibits the reaction. NMP as a polar solvent gives the best results. The use of tri(2-furyl)phosphine and Ph As in the coupling of stannanes with the halides and triflates increases the rate of the transmetallation of the stannanes to Pd, which is thought to be the rate-... [Pg.70]

The carbonylation of aryl iodide in the presence of terminal alkynes affords acyl alkynes. Bidentate ligands such as DPPF give good results [241]. When PI13P is used, phenylacetylene is mainly converted to diphenylacetylene. The alkynyl ketones 488 are prepared by the reaction of the alkenyl triflate 487 with phenylacetylene and CO [242],... [Pg.92]

Me2CuLi couples with a variety of alkenyl triflates (bromides, iodides) giving methyl derivatives (Table 16.1), and, in complete analogy, with aryl triflates (bromides, iodides). Occasionally, Me2CuLi also couples with alkenyl or aryl phosphates. [Pg.692]

Many alkenyl triflates (-bromides, -iodides) may be prepared with cis- or trans- and E- or Z-configuration, respectively ... [Pg.692]


See other pages where Alkenyl triflate is mentioned: [Pg.230]    [Pg.242]    [Pg.234]    [Pg.235]    [Pg.380]    [Pg.320]    [Pg.440]    [Pg.244]    [Pg.246]    [Pg.798]    [Pg.19]    [Pg.63]    [Pg.119]    [Pg.122]    [Pg.128]    [Pg.91]    [Pg.340]    [Pg.988]    [Pg.693]   
See also in sourсe #XX -- [ Pg.149 ]

See also in sourсe #XX -- [ Pg.243 , Pg.540 , Pg.691 , Pg.692 , Pg.693 , Pg.709 , Pg.714 , Pg.721 , Pg.724 , Pg.726 , Pg.731 ]

See also in sourсe #XX -- [ Pg.160 ]




SEARCH



Alkenyl triflates

Alkenyl triflates alkenylation

Triflates alkenylation

© 2024 chempedia.info