Selective Alkynylallylation of the C−C σ Bond of Cyclopropenes

Abstract

AP d-catalyzed regio-and stereoselective alkynylallylation of as pecific C À C s bond in cyclopropenes,u sing allyl propiolates as both allylation and alkynylation reagents, has been achieved for the first time.B ym erging selective C(sp 2)-C(sp 3)b ond scission with conjunctive cross-couplings, this decarboxylative reorganization reaction features fascinating atom and step economy and provides an efficient approach to highly functionalizedd ienynes from readily available substrates.W ithout further optimization, gram-scale products can be easily obtained by such as imple,n eutral, and low-cost catalytic system with high TONs.D FT calculations afford ar ationale toward the formation of the products and indicate that the selective insertion of the double bond of cyclopropenes into the C-Pd bond of ambidentate Pd complex and the subsequent nonclassical b-C elimination promoted by 1,4palladium migration are critical for the success of the reaction. Scheme 1. Pd-catalyzed selective alkynylallylation of the CÀC s bond in tetrasubstituted cyclopropenes.

Selective Alkynylallylation of the C−C σ Bond of Cyclopropenes

“…Forthe efficient synthesis of 3u and 3v from cyclopropenes with electron-deficient double bond, the ligand P(p-CF 3 C 6 H 4 ) 3 needed to be replaced with ar elatively more electron-donating ligand P(2-furyl) 3 .T of urther confirm the structure of the products,w em easured the single crystals of 3j, 3u,a nd 3v,r espectively. [16] These results demonstrated that the selectivity of representative product 3jwas consistent with our inference from the model reaction and the s-bond selectivity of the reaction is not reversed by the enhance of steric effect (from 3uto 3v). It should be noted that some 1,1dicyanocyclopropenes cannot be smoothly used in this transformation even if the conditions were further optimized ( Figure 1).…”

“…An acetonitrile solution of the substrates in the presence of 2.5 mol %P d 2 (dba) 3 and 15 mol %P ( p-CF 3 C 6 H 4 ) 3 at 70 8 8Cf urnished the desired product 3a in 88 %i solated yield (entry 1), and its structure was confirmed by single-crystal X-ray diffraction. [16] This model reaction exhibited outstanding chemo-, regio-, and stereoselectivity.N one of the other isomers had been found by the rough NMR or LC-MS testing.C ontrol experiments established the importance of P(p-CF 3 C 6 H 4 ) 3 (entries 2-4). Appropriate Pd to ligand ratio was critical for the efficient formation of the target molecule (entry 5).…”

“…Yield of isolated product. [16] Angewandte Chemie Forschungsartikel the product was unique.T he ratio mainly depended on the combined effect of the electron pushing and pulling ability of the groups at C2 and C3. Even the weak polarity of the double bond can lead to significant s-bond selectivity of the reaction.…”

“…In order to take full advantage of the structural characteristics of most products,t hat is,h aving two controllable aryls on the same side of the tetrasubstituted alkenes,we made use of the air-driven oxidative photocyclization developed by Watanabesg roup [11] for efficiently constructing specific position functionalized phenanthrenes,which are not easy to be obtained through other ways.W ith or without substituents on its benzene rings,the compound 3 was able to successfully participate in the oxidative cyclization (4a-4f)to offer as ingle product in good to excellent yield. It is worth mentioning that the configuration of representative product 4a was determined by X-ray diffraction [16] and the reaction of 3q also exhibited satisfactory regioselectivity that was regu-…”

Visible-Light-Induced Organocatalyzed [2+1] Cyclization of Alkynes and (Trifluoroacetyl)silanes

“…Due to their unique properties caused by ring tension (about 54.1 kcal/mol), 1 cyclopropenes have been utilized as useful intermediates in organic synthesis. 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Consequently, many methods have been developed for their synthesis. 2–23 The carbene-transfer reaction between diazo compounds and alkynes has been among the most popular methods for the synthesis of cyclopropenes.…”