13C magnetic resonance studies. 142. The fate of highly substituted acyclic ketones in strong base: β-enolization, Haller–Bauer cleavage, and an alkyl to aryl acyl shift

1990 ◽  
Vol 68 (7) ◽  
pp. 1106-1115 ◽  
Author(s):  
Rainer A. Dyllick-Brenzinger ◽  
Vijay Patel ◽  
Mollin B. Rampersad ◽  
J. B. Stothers ◽  
Shirley E. Thomas
Keyword(s):  
Magnetic Resonance ◽  
Proton Exchange ◽  
Methyl Groups ◽  
Strong Base ◽  
Proton Abstraction ◽  
Magnetic Resonance Studies ◽  
Significant Process ◽  
Cyclic Systems ◽  
Acyclic Ketones ◽  
Butyl Ketone

Di-tert-butyl ketone (2a), 5,5,7,7-tetramethyl-6-undecanone (2b), and 2,4-dimethyl-2,4-diphenyl-3-pentanone (2d) have been found to undergo slow rearrangement by β-proton abstraction from the α-methyl groups upon treatment with t-BuO−/t-BuOH/≥ 185 °C. This is in contrast to the absence of such rearrangement in cyclic systems. It is the only significant process observed for 2a and 2b, whereas with 2d and its monomethyl analog 22 Haller–Bauer type cleavage and an unprecedented 1,3-acyl shift from sp3 to sp2 carbon accompany the β-enolate rearrangement. The rates of 1H/2H exchange of the methyl protons in 2a, b were found to be similar to those reported for a variety of cyclic systems but this exchange does not occur in 2d, where only aryl proton exchange was observed. Keywords: β-enolization, acyclic ketones, acyl shift.

scholarly journals β-Enolization in α-phenyl-α,α′,α′-trimethylcycloalkanones

1992 ◽  
Vol 70 (5) ◽  
pp. 1274-1280 ◽  
Author(s):  
Wendy Sifton ◽  
J. B. Stothers ◽  
Shirley E. Thomas
Keyword(s):  
Secondary Alcohol ◽  
Ring Expansion ◽  
Methyl Groups ◽  
Proton Abstraction ◽  
Phenyl Proton ◽  
Methyl Derivatives ◽  
Cyclic Systems ◽  
A Minor ◽  
Acyclic Ketones ◽  
Derivatives Of

Ring expansion through β-proton abstraction from α-methyl groups has been observed for the α-phenyl-α,α′,α′,-tri-methyl derivatives of cyclopentanone and cyclohexanone upon treatment with t-BuO−/t-BuOH/185 °C. This contrasts with the lack of rearrangement found for the α,α,α′,α′-tetramethyl derivatives but is analogous to the behavior of some α-phenyl acyclic ketones. However, this process is reversible in the cyclic systems, but irreversible in the acyclic cases. For all of these α-phenyl substituted ketones, rearrangement is in competition with Haller–Bauer type cleavage. In the cyclic systems, a minor process was observed whereby some of the ring-expanded product is reduced to the corresponding secondary alcohol but there was no evidence of rearrangement through γ-enolate formation involving phenyl proton abstraction, which is a minor process in the α-phenyl acyclic systems.

13C Nuclear Magnetic Resonance Studies of Organometallic Compounds. V. Di- and Trimethylplatinum(IV) Derivatives

1974 ◽  
Vol 52 (10) ◽  
pp. 1973-1982 ◽  
Author(s):  
Howard Charles Clark ◽  
Leo Ernest Manzer ◽  
John Edward Henry Ward
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Organometallic Compounds ◽  
Methyl Groups ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Cis And Trans ◽  
Nuclear Magnetic

The 13C n.m.r. parameters for thirteen di- and trimethylplatinum(IV) derivatives have been obtained. It is shown that the 13C shieldings and 1JPtC and 2JPtCH values of methyl groups both cis and trans to varied ligands consistently follow trends similar to those found for related methylplatinum(II) derivatives.

13C Nuclear Magnetic Resonance Studies of Organometallic Compounds. IV. cis-Dimethylplatinum(II) Derivatives

1974 ◽  
Vol 52 (7) ◽  
pp. 1165-1170 ◽  
Author(s):  
Howard Charles Clark ◽  
Leo Ernest Manzer ◽  
John Edward Henry Ward
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Organometallic Compounds ◽  
Methyl Groups ◽  
Magnetic Resonance Studies ◽  
Trans Influence ◽  
13C Nuclear Magnetic Resonance ◽  
Cis And Trans ◽  
Derivatives Of ◽  
Nuclear Magnetic

Data derived from the 13C n.m.r. spectra of seven neutral cis-dimethylplatinum(II) derivatives of the type cis-(CH3)2PtL2 and cis-(CH3)2Pt(L—L) (where L and L—L are neutral donors) are discussed and compared with data derived from the 1H n.m.r. spectra of the complexes. Simultaneous variations in L or L—L reveal that the n.m.r. trans-influence rather than the n.m.r. cis-influence is dominant. The suggestion that the n.m.r. cis- and trans-influences may be additive is discussed. In contrast with data obtained by other workers, it is shown that the 1JCH values of the platinum methyl groups are essentially insensitive to variations in the remaining ligands.

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