Allenic amides

Starting with bromoallenes 133, nucleophilic substitution supported by the use of cuprous cyanide lead to cyanoallenes of type 134 (Scheme 7.22) [126, 131, 181]. Pro-pargyl precursors and also cumulenes of type 133 can be utilized for palladium-catalyzed aminocarbonylation to give allenic amides 135 (cf. Section 7.2.6) [182]. 

Several trivial but highly useful reactions are known to convert one acceptor-substituted allene into another. For example, the transformation of allenic carboxylic acids is possible both via the corresponding 2,3-allenoyl chlorides or directly to 2,3-allen-amides [182,185], Allenylimines were prepared by condensation of allenyl aldehydes with primary amines [199]. However, the analogous reaction of allenyl ketones fails because in this case the nucleophilic addition to the central carbon atom of the allenic unit predominates (cf. Section 7.3.1). Allenyl sulfoxides can be oxidized by m-CPBA to give nearly quantitatively the corresponding allenyl sulfones [200]. The reaction of the ketone 144 with bromine yields first a 2 1 mixture of the addition product 145 and the allene 146, respectively (Scheme 7.24). By use of triethylamine, the unitary product 146 is obtained [59]. The allenylphosphane oxides and allene-... 

With catalysis by tetrakis(triphenylphosphane)palladium(0), the reaction of allenic amides 275 and aryl or vinyl iodides afforded Z-configured iminolactones 277... 

Contrary to the phosphine-catalyzed reaction of the allene buta-2,3-dienoate, which adds to CgQ in a ]3-i-2] cycloaddihon ]354], the allene amide 317 forms the cyclobutane annulated fuUerene derivahve in good yields (Scheme 4.63) [355]. The reaction was also performed with similar allene amides bearing a six- or seven-membered lactam. 

The formation of compound 175 could be rationalized in terms of an unprecedented domino allene amidation/intramolecular Heck-type reaction. Compound 176 must be the nonisolable intermediate. A likely mechanism for 176 should involve a (ji-allyl)palladium intermediate. The allene-palladium complex 177 is formed initially and suffers a nucleophilic attack by the bromide to produce a cr-allylpalladium intermediate, which rapidly equilibrates to the corresponding (ji-allyl)palladium intermediate 178. Then, an intramolecular amidation reaction on the (ji-allyl)palladium complex must account for intermediate 176 formation. Compound 176 evolves to tricycle 175 via a Heck-type-coupling reaction. The alkenylpalladium intermediate 179, generated in the 7-exo-dig cyclization of bro-moenyne 176, was trapped by the bromide anion to yield the fused tricycle 175 (Scheme 62). Thus, the same catalytic system is able to promote two different, but sequential catalytic cycles. 

An interesting and truly catalytic cycloisomerization reaction of a-allenic amides was also reported recently which, however, afforded mixtures of 2-(5//)-furanylidenamines and l,5-dihydro-2//-pyrrol-2-ones in most cases.339 339a... 

Hydration of attenic nitriles. 4,4-Dialkyl-substitutcd allenic nitriles (1) are converted into allenic amides (2) in 60 70% yield by reaction with hydrogen peroxide in alcoholic sodium hydroxide. 

Alkynes and allenes also react with amides. Phenylthiomethyl alkynes were converted to A-Boc-A-phenylthio allenes with Boc azide and an iron catalyst. The palladium-catalyzed reaction of an allene amide, with iodobenzene, leads to A-sulfonyl aziridines having an allyhc group at Other allene A-tosylamines... 

Propargylsilanes show predictable behavior as cyclizadon terminators. Internal additions of propy-nylsilanes to acyclic )V-acyliminium ions promoted by Lewis acids or prodc acids yield a-allenic amides or carbamates (Scheme 54). ... 

The intramolecular acid-catalyzed reacdon of 2-propargylsilanes of structural type (117) with N-acy-liumion ion precursors leads to bridged azabicyclic ring systems (118 Scheme 33) which contain an a-allenic amide fimcdon. These bicyclic products serve as intermediates to highly funcdonalized trans-fused ring systems possessing a 1,3-diene moiety. 

Alkynoic esters, 493-494 Alkynyldiethyl alanes, 144 Allene cyclo-oligomerization, 41 Allenes, 161,315-316,438 Allenic adds, 149-150 Allenic amides, 255... 

Reaction of propargyltrimethylsilane with oj-ethoxylactams under the influence of boron trifluoride affords (u-allenyllactams. The intramolecular version of this process gives rise to bridged azabicyclic systems containing the uncommon a-allenic amide functionality (equation 8). ... 

Figure 2.59 collects several [2t-2]-cycloadditions that can be carried out with C )-The reaction with dehydrobenzene is instructive as it reveals electronic properties of the fullerene The dehydrobenzene generated in situ from anthranilic acid reacts with Cso exclusively in a [2-i-2]-cycloaddition, although in principle a [4-f2]-reaction would also be possible, and dehydrobenzene usually enters into the latter when adding to electron-rich dienes. The nonoccurrence of this reaction clearly shows the electron-deficient character of C,so. For the same reason it never constitutes the diene part in a Diels-Alder reaction. Furthermore, the [24-2]-cycloaddition may be thermally effected, for example, the addition of long-chain cumulenes, allene amides or quadricyclan. The addition of ketenes as well occurs without irradiating the reaction mixture. Normally a reduced reactivity toward C,so should be expected for the electrophilic ketenes, but in reality the products of a [2-1-2]-cycloaddition are even found to be the major product. 

Isomerization reactions of 2-ynoic acids [59] and P-allenic amides [60] also provide suitable methodologies for the preparation of conjugated amides. The former compounds are isomerized by catalysis with ruthenium or iridium complexes and allow the synthesis of pellitorine (1), Achillea amide (4) and trichonine (13) (Scheme 15). 

The reaction of propargyl alcohols with amide acetals gives P-allenic amides, which can be isomerized to (2 ,4 )- [32] or (2 ,4Z)-dienamides [60] such as piperine (25) [32] and isochavicine (28) [60] (Scheme 16). 

Allenes, 57, 285, 286, 356 Allcnic aldehydes, 189-190 Allenic amides, 169 AUenic boranes, 285, 286 Allenic esters, 301 Allenic ethers, 320 Allenic ketones, 189-190, 301 Allenic sulfones, 395 Allylacetophenone, 7-8 AUylbenzene, 292 Allyl bromide, 133, 292 Allyl diazoacetate, 222 Allyl esters, 302 Allyl ethers, 136-137 Allylic acetates, 176, 534 Allylic alcohols, 6, 136, 141, 142, 179, 191, 260, 335, 346, 373, 379-380, 427, 428, 445, 451-452,534 r-AUylic alcohols, 426-427 Allylic amination, 43 Allylic amines, 176 Allylic carbamates, 316 Allylic chlorides, 516 Allylic esters, 173, 243 Allylic ethers, 534 Allylic halides, 334-335 Allylic hydroperoxides, 247, 316, 317, 370... 

Tertiary allenic amides, Diethylformamide acetals react with propargyl alcohols in refluxing xylene or dichlorobenzene (with removal of the alcohol) to form allenic amides in variable yields. ... 

A general, high-yielding route to terminal allenic amides (160) is the reaction between propargylic alcohols and diethylformamide acetals,while some success has been achieved in the synthesis of potentially insecticidal 2,4,5-trienamides (161) by a Wadsworth-Emmons type reaction between substituted buta-2,3-dienals and carbamoylmethylphosphonates. ... 

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