Addition von Organomagnesiumhalogeniden an CC‐Bindungen, IX¹⁾ Regioselektivität der Addition von Organomagnesiumhalogeniden an 1‐Alkene

Abstract

Es wird die Additionsrichtung von 2-Alkenyl-, Benzyl-, sek.-und tert.-Alkylmagnesiumhalogeniden 1-8 an 1-Alkene untersucht und eine Abhangigkeit des Verhaltnisses von (Metall-an-C-2-)-zu (Metall-an-C-])-Addition von GroDe und Richtung der induktiven Effekte der Gruppen R1 -R3 des Organomagnesiumhalogenids HalMgCRlR2R3 festgestellt. Bei einer Anhaufung von Methylgruppen (+I-Effekt) am C-Atom, das am Metall gebunden ist (R1= R2 = R3 = CH3)addiert sich das Metall zu 99 %an das C-2. Ersetzt man sukzessive Methylgruppen durch H, Vinyl-oder Phenylgruppen f-I-Effekt), so nimmt der Anteil der Metallanlagerung an das C-1 zu und macht bei R1 = R2 = H und R3 = Vinyl oder PhenyI gegenuber alkylsubstituiertem Athylen [I-Octen (9) oder 1-Nonen (44)] 100 % aus. Das Verhaltnis der Produkte aus beiden Additionsrichtungen 12Dt sich mit der Summe der Taft-Konstanten der Reste R1, R2 und R3 korrelieren. Die Beziehung zwischen dem Logarithmus des Produktverhaltnisses aus (Metall-an-C-2)-und (Metall-an-C-])-Addition und der Summe der ahn-Werte ist annahernd linear. -An Styro! (45) lagert sich das Magnesium der untersuchten Organomagnesiumhalogenide 1, 2, 3, 5, 6 und 8 uberwiegend an C-2 an. Das Verhaltnis der Produkte ist ebenfalls von der Summe der cr*-Werte der Reste R1-R3 abhangig. Da die Addition der 2-Alkenylverbindungen an Styrol jedoch reversibel ist, lagern sich primar gebildete Addukte mit Metall am C-1 langsam in die thermodynamisch stabileren Benzylverbindungen mit Metall am C-2 um. Addition of Organomagnesium Halides to C=C Bonds, 1x1). -Regioselectivity of Addition of Organomagnesium Halides to 1-AlkenesThe direction of addition of 2-alkenyl-, benzyl-and of sec-and tert-alkylmagnesium halides 1-8 to 1-alkenes has been investigated. A correlation is observed between the ratio of metal-to-C-2 and metal-to-C-1 addition and the direction and magnitude of the inductive effects associated with the groups R1 to R 3 present in the organomagnesium halide,HalMgCRlRZR3. An accumulation of methyl groups (+I effect) on the metal bonded C atom (R1 = R* = R3 = CH3) results in up to 99 % addition of metal to C-2. Successive replacement of the methyl groups by H, vinyl or phenyl groups (-1 effect) causes an increase in the extent of addition of metal to C-l which amounts to 100% with alkyl-substituted ethylene *) Korrespondenz bitte an diesen Autor richten. I

Reactions of Cyclopropenes with Organoaluminum Compounds and Other Organometallic Compounds: Formation of Ring-Opened Products

“…(2) Although t -Bu 2 Mg did not react with 7 , it did react with much less hindered 23 . Product 24 resulted from a syn addition; attachment of the tert -butyl group was to the less substituted carbon of 23 , which is the reverse of the usual orientation of additions of polar organometallic compounds to alkenes but an orientation that has been observed for additions to other alkenes of hindered organometallics, including a tert -butyl Grignard reagent . The other product of this reaction, 25 , could result from electrophilc attack and rearrangement ( 38 → 39 → 40 ) as proposed for reactions with Et 3 Al.…”

Additions and cycloadditions of 2-phenylallylmagnesium phenoxide to carbon-carbon double bonds

“…Its yield maximized at 43% after 1.0 min. It was isolated by GLC on column C at 300 °C and was identified by 220-MHz NMR and mass spectra as 12 3.73 (m, Hc), 5.14 (s, Hg), 5.26 (s, Hf), 7.1-7.6 (m, 11 H); mass spectrum m/e (rel intensity) 270 (5), 253 (3), 189 (2), 165 (16), 154 (30), 153 (100), 152 (100), 127 (4), 126 (5), 115 (22).…”

“…2-[(E)-2-Phenylethenyl]-4,4-dimethyloxazoline (18). By a general procedure33 0.44 mol of 2-amino-2-methyl-l-propanol and 0.22 mol of cinnamoyl chloride gave a 67% yield of iV-(2,3-dimethyl-3-hydroxypropyl)cinnamide (22), mp 133-134 °C.…”