- Regio- and stereoselective synthesis of bromoalkenes by homolytic hydrobromination of alkynes with hydrogen bromide
-
Homolytic hydrobromination of terminal and internal alkynes with a commercially available solution of hydrogen bromide in acetic acid has been investigated for regio- and stereoselective synthesis of bromoalkenes. Under an aerobic atmosphere at room temperature, the reaction of ethynylarenes with a small excess of HBr efficiently gave (2-bromoethenyl)arenes with good to high E-selectivity. (Alk-1-ynyl)arenes, or internal alkynes bearing both phenyl and alkyl groups at the sp-carbons also underwent the air-initiated hydrobromination to exhibit high Z-selectivity under kinetic conditions using a half equivalent of HBr.
- Kumaki, Wataru,Kinoshita, Hidenori,Miura, Katsukiyo
-
-
- Chemoselective Homologation-Deoxygenation Strategy Enabling the Direct Conversion of Carbonyls into (n+1)-Halomethyl-Alkanes
-
The sequential installation of a carbenoid and a hydride into a carbonyl, furnishing halomethyl alkyl derivatives, is reported. Despite the employment of carbenoids as nucleophiles in reactions with carbon-centered electrophiles, sp3-type alkyl halides remain elusive materials for selective one-carbon homologations. Our tactic levers on using carbonyls as starting materials and enables uniformly high yields and chemocontrol. The tactic is flexible and is not limited to carbenoids. Also, diverse carbanion-like species can act as nucleophiles, thus making it of general applicability.
- Citarella, Andrea,Holzer, Wolfgang,Ielo, Laura,Langer, Thierry,Miele, Margherita,Pace, Vittorio,Urban, Ernst,Zehl, Martin
-
supporting information
p. 7629 - 7634
(2020/10/12)
-
- A mild synthesis of vinyl halides and gem-dihalides using triphenyl phosphite-halogen-based reagents
-
A new application of (PhO)3P-halogen-based reagents to the synthesis of vinyl halides and gem-dihalides is described. Vinyl halides were prepared in good to excellent yields from enolizable ketones, whereas aldehydes afforded the corresponding gem-dihalides. The halogenation proceeded smoothly under mild conditions.
- Spaggiari, Alberto,Vaccari, Daniele,Davoli, Paolo,Torre, Giovanni,Prati, Fabio
-
p. 2216 - 2219
(2007/10/03)
-
- Discrimination of enantiotopic iodine atoms by an iodine/magnesium exchange reaction
-
An enantioselective iodine/magnesium exchange reaction between the diiodoalkane 4 and a chiral Grignard reagent 12 has been realized at -78°C in THF. The resulting α-iodoalkylmagnesium reagents 13 are configurationally stable under these conditions and during trapping by a benzaldehyde/dimethylaluminium chloride system to furnish the iodohydrins 19 and epoxides 9.
- Schulze, Volker,Hoffmann, Reinhard W.
-
p. 337 - 344
(2007/10/03)
-
- Brominative Deoxygenation of Some Aldehydes and Ethers
-
Three aldehydes (4a-c) are transformed into 1,1-dibromides (6a-c) by 2,2,2-tribromo-2,2-dihydro-1,3,2-benzodioxaphosphole (2).This reagent (2) is also very active in the cleavage of ethers; its reactions may show some features of carbonium as well as of SN2 character.
- Roman, Ulrich von,Knorr, Rudolf,Behringer, Claudia,Ruhdorfer, Jakob
-
p. 260 - 262
(2007/10/02)
-
- Synthesis of 1,1-Dihaloalkanes
-
The reaction of 1,1-bistrifluoromethylsulfonyloxy-alkanes (2) with magnesium iodide in carbon disulphide at O deg C affords 1,1-diiodoalkanes (3-I) in good yields.No rearrangement products are observed.The reaction of 2 with magnesium bromide in carbon disulphide or titanium tetrachloride in dichloromethane yields either 1,1-dichloro- (3-Cl) or 1,1-dibromoalkanes (3-Br).Rearrangements products are formed from α-branched substrates.
- Garcia Martinez, A.,Herrera Fernandez, A.,Martinez Alvarez, R.,Garcia Fraile, A.,Bueno Calderon, J.,et al.
-
p. 1076 - 1078
(2007/10/02)
-