7624-24-0Relevant articles and documents
Acyl-carbene and methyl-carbene coupling via migratory insertion in palladium complexes
Meana, Isabel,Albeniz, Ana C.,Espinet, Pablo
, p. 5494 - 5499 (2012/11/07)
The migratory insertion reaction of a carbene into a palladium-acyl bond has been observed both for monoaminocarbenes and for methoxycarbenes. The acyl derivative [PdCl(COMe){C(NEt2)Ph}(PPh3)] undergoes an acyl-carbene coupling, leading to the enolate-type complex [PdCl{C(COMe) (NEt2)Ph}(PPh3)]2 (2). This complex decomposes either by reductive elimination to give the iminium salt or by protonation of the enolate to give a ketoamine. In a similar fashion, the reaction of [Pd 2(μ-Cl)2(COMe)2(SMe2) 2] with [W(CO)5{C(OMe)Ph}] leads to an undetected palladium enolate that, after protonation, is stabilized by coordination to palladium ([PdCl2{(OH)MeC=CPh(OMe}(SMe2)], 8). The reaction of [Pd2(μ-Cl)2Me2(SMe 2)2] with [W(CO)5{C(OMe)-Ph}] leads to the migratory insertion of the carbene into the Pd-methyl group to give an alkyl palladium complex. The transfer of CO from tungsten, followed by insertion into the Pd-Me group, also occurs. This leads to the formation of a Pd-COMe group, which also undergoes migratory insertion of the carbene fragment. These results support that migratory insertion is a key C-C coupling step, as proposed for the new Pd-catalyzed transformations that use carbene precursors.
Generation and trapping of allene oxides: An approach to chiral, nonracemic α-alkoxyketones
Shipman, Michael,Thorpe, Heidi R.,Clemens, Ian R.
, p. 14265 - 14282 (2007/10/03)
Epoxy mesylates 5 react with a variety of sodium alkoxides to produce the corresponding α-alkoxyketones in good yields. Evidence is presented for the involvement of transient allene oxides in these reactions. Enantiomerically enriched epoxy mesylates (2R,3S)-5a-c were prepared using the Sharpless asymmetric epoxidation reaction as the key step. These precursors rearrange to α-alkoxyketones without significant racemisation under modified reaction conditions (ROK, 18-crown-6, THF, -78°C). The reactions are shown to proceed with stereochemical inversion at the epoxide centre.
Novel and efficient insertions of carbons carrying O-, S-, and N-Linked substituents: Synthesis of α-alkoxyalkyl, α-(Alkylthio)alkyl, and α-(Carbazol-9-yl)alkyl ketones
Katritzky, Alan R.,Xie, Linghong,Serdyuk, Larisa
, p. 7564 - 7570 (2007/10/03)
A wide variety of benzotriazolyl-stabilized anions 2, obtained by the lithiation of 1-(α-alkoxyalkyl)-, 1-[α-(alkylthio)alkyl]-, and 1-[α-(carbazol-9-yl)alkyl]benzotriazoles 1, on reaction with aliphatic and aromatic aldehydes and ketones, followed by rearrangement induced by heating in the presence of zinc bromide, furnish one-carbon-homologated α-alkoxyalkyl, α-(alkylthio)alkyl, and α-(carbazol-9-yl)alkyl ketones 4 in simple one-pot operations in good yields with excellent regioselectivity. In several alkoxymethylene insertions, intermediate 2-alkoxyoxiranes were separated in good yields, demonstrating the epoxide mechanism for the rearrangements and providing a facile approach to poly substituted 2-alkoxyoxiranes, another class of important compounds.
α-Umpolung of Ketones via Enol Cation Radicals. Mechanistic and Synthetic Aspects
Schmittel, Michael,Levis, Michael
, p. 1935 - 1938 (2007/10/02)
The novel α-Umpolung of ketones via intermediate enol cation radicals has been explored mechanistically and tested for different nucleophiles that are compatible to the oxidative conditions.The rate of the reaction was determined indicating that enolizati
A UNIQUE 1,2-SHIFT SELECTIVITY IN 2-HYDROXYPROPIOPHENONE DIMETHYLACETALS: GENERATION OF NEW METHODOLOGIES FOR METHYL-2-ARYLPROPANOATES AND 1,2-CARBONYL TRANSPOSITION
Sonawane, H. R.,Nanjundiah, B. S.,Kulkarni, D. G.,Ahuja, Jaimala R.
, p. 7319 - 7324 (2007/10/02)
α-Hydroxydimethylacetals I have been shown to undergo two different rearrangements involving highly selective 1,2-shifts under mild conditions.When treated with Ph3P/CCl4 in the presence of pyridine, I were cleanly transformed via 1,2-aryl shifts into methyl 2-arylpropanoates, an important class of antiinflammatory agents; a pronounced substituent effect has been observed in this rearrangement. On the other hand, treatment of I with catalytic amount of Ph3P/I2 in benzene furnished α-methoxy-α-aryl propan-2-ones in excellent yields and culminated in the development of a new methodology for 1,2-carbonyl transposition.
THE NEF REACTION ON TRIALKYLSILYL NITRONATES PROMOTED BY m-CHLOROPERBENZOIC ACID, AN EFFICIENT ROUTE TO α-ALKOXYKETONES FROM NITROALKANES
Aizpurus, J. M.,Oiarbide, M.,Palomo, C.
, p. 5361 - 5364 (2007/10/02)
Treatment of a nitroalkene with nucleophiles, followed by silylation of the resulting nitroalkane and subsequent treatment with m-chloroperbenzoic acid provides α-functionalized carbonyl compounds in good yields.
The Favorskii Rearrangement of α-Chloro Ketimines
Kimpe, Norbert De,Sulmon, Paul,Moeens, Luc,Schamp, Niceas,Declercq, Jean-Paul,Meerssche, Maurice Van
, p. 3839 - 3848 (2007/10/02)
The Favorskii rearrangement of α-chloro ketimines has been studied.It was shown that the base-induced rearrangement of α-chloro ketimines afforded imidates or amides via a mechanism involving 1,3-dehydrochlorination and ring-opening of the resulting cyclopropylideneamines.The ring-opening occurred in such a way as to produce the most stable carbanion.The entire mechanism paralleled the well-known cyclopropanone mechanism of the Favorskii rearrangement of the corresponding oxygen analogues, i.e., α-halo ketones.Evidence has been presented that the semibenzilic-type mechanism is not operative in the cases studied.Depending upon the reaction conditions and the substrate, the Favorskii rearrangement was accompanied by various side reactions including nucleophilic substitution, 1,2-dehydrochlorination, rearrangement via intermediate α-alkoxyaziridines, and self-condensation.
A NEW APPROACH TO α-ALKOXY- AND α-ALKYLTHIOKETONES FROM CONJUGATED NITROALKENES
Varma, Rajender S.,Kabalka, George W.
, p. 443 - 450 (2007/10/02)
α-Substituted ketones are obtained in two steps by reduction of the α,β-unsaturated nitroalkenes using SnCl2*2H2O in alcoholic media followed by hydrolysis with levulinic acid.
TRANSFORMATIONS OF 1,1-DIMETHOXY-2-PHENYLCYCLOPROPANE UNDER THE INFLUENCE OF PROTIC ACIDS
Novokreshchennykh, V. D.,Lukashova, E. A.,Mochalov, S. S.,Shabarov, Yu. S.
, p. 2022 - 2027 (2007/10/02)
Under the influence of protic acids 1,1-dimethoxy-2-phenylcyclopropane undergoes opening of the three-membered ring, the direction of which does not depend on the strength or the nature of the acid but varies with the polarity of the solvent.In acid-solvent systems which exhibit oxidizing characteristics the compound can undergo oxidative cleavage of the cyclopropane ring directly.
Electrochemical Reduction and Oxidation of Allenes
Schlegel, Guenter,Schaefer, Hans J.
, p. 960 - 969 (2007/10/02)
The allenes 1 - 3 are reduced on mercury at -2.17 V (sce) (1), -3.12 V (2), and below -3.30 V (3); they are oxidized on glassy carbon at 1.25, 1.65 V (1), 1.75 V (2), and above 2.25 V (3).In the preparative reduction 1 forms, depending on the workup, 86percent of 1,1,3,3-tetraphenyl-1-propene (6a) or up to 50percent of aldehyde 9, a formylation product of the rearranged radical anion intermediate; on carboxylation of the electrolyte 54percent of carboxylic acid 8 are formed.The allene 2 is hydrogenenated to give 30 percent of (E)-1-phenyl-1-propene (10) and hydrodimerized to form 30percent of yield s in methylene dichloride/methanol 61 - 73percent of 2-chloro-1,1,3-triphenylidene (13), which is probably formed by chlorine, that is electrochemically generated from methylene chloride.In methanol/dioxane 13 is not obtained but 71percent of indanone 16 are produced.The oxidation of 2 and 3 is unselective; due to follow-up oxidations many products are formed in low yield.
