75111-04-5Relevant academic research and scientific papers
Asymmetric synthesis of α-allenylglycines
Bucuroaia, Carmen,Groth, Ulrich,Huhn, Thomas,Klinge, Michael
experimental part, p. 3605 - 3612 (2009/12/01)
The coupling of the homocuprate of the bislactim ether of cyclo-(-L-Val-Gly-) (9) with primary propargyl halides produces the allenyl-substituted bislactim ethers 11 in a highly diastereoselective manner, whereas the alkylation of the lith-iated bislactim ether of cyclo-(-L-Val-Gly-) yields the proparg-yl-substituted bislactim ethers 12. Subsequent hydrolysis affords, after protection of the amino group, the methyl α- allenylglycinates 15, the α-allenylglycines 16, and the methyl α-propargylglycinates 17.
Cycloaddition Reactions of Strained Ring Systems. Photochemistry of 1-Phenyl-2-carbomethoxy-3,3-dimethylcyclopropene
Padwa, Albert,Kennedy, G. Davon
, p. 4344 - 4352 (2007/10/02)
The sensitized irradiation of 1-phenyl-2-carbomethoxy-3,3-dimethylcyclopropene produced two novel photodimers.The minor product can be explained in terms of an initial bond formation to give a diradical intermediate.Collapse of the diradical furnishes a tricyclohexane which undergoes a subsequent cycloreversion to give a 1,4-cyclohexadiene derivative.The major photodimer is derived by cyclopropyl ring opening of the initially produced diradical followed by cyclization to give a bicyclobutane derivative.Direct irradiation of 1-phenyl-2-carbomethoxy-3,3-dimethylcyclopropene afforded a mixture of 1-carbomethoxy-3,3-dimethyl-1-phenylallene, 1-carbomethoxy-3-methyl-2-phenylbutadiene, and 2-carbomethoxy-3-methyl-1-phenylbutadiene.The formation of the three products can be rationalized in terms of a vinylcarbene intermediate which inserts into the adjacent methyl group.The product distribution favors cleavage of the carbomethoxy substituted ?-bond of the cyclopropene ring.This regioselectivity can be attributed to a funneling of the excited singlet state of the cyclopropene to the energy surface of the higher lying carbene state.The photochemical and thermal behavior of several hydroxyalkyl substituted cyclopropenes derived from 1-phenyl-2-carbomethoxy-3,3-dimethylcyclopropene was also studied and the results obtained were compared to the reactions in the carbomethoxy series.
Cycloaddition Reactions of Allenyl Cations with Cyclopentadiene
Mayr, Herbert,Halberstadt-Kausch, Inge K.
, p. 3479 - 3515 (2007/10/02)
Propargyl halides R1-C=-C-CR2R3X (14) and cyclopentadiene react with zinc halide catalysis in ether/dichloromethane solution to give 3-halogenobicycloocta-2,6-dienes 13 (R1 = alkyl) or 5-(α-halogenobenzylidene)norbornenes 15 (R1 = aryl).The reactions are interpreted by stepwise - and -cycloadditions of intermediate allenyl cations 1, proceeding via propargylcyclopentenyl cations 5 and bicyclic vinyl cations 9 or 12.If the reactions are initiated by equimolar amounts of silver trifluoroacetate, quenching products of all postulated intermediates are isolated.The relative energies of the intermediate carbenium ions are estimated on the basis of force field calculations and of gas phase stabilities of simple carbocations.Stereochemical studies indicate that the addition reactions proceed via the compact transition state 42 rather than 41.The zinc chloride catalysed reaction of propargyl chloride 14e with cyclopentadiene yields the 2:1 product 17 (structurally assigned by X ray analysis) in addition to the 1:1 product 15e.The formation of 17 is rationalised by a -cycloaddition of allenyl cation 1 with cyclopentadiene.
