Bin Liu

Date of Graduation


Document Type



1,2,3-Butatrienes ( (3) cumulenes) were synthesized via 1,4-eliminations of hydroxytrimethylsilanes from 4-(trimethylsilyl)-2-butyn-1-ols. The precursors, 4-(trimethylsilyl)-2-butyn-1-ols, were easily prepared from a propargylic trimethylsilane and an aldehyde or a ketone. Treatment of the propargylic trimethylsilane in THF with n-butyllithium followed by condensation with an aldehyde or a ketone afforded 4-(trimethylsilyl)-2-butyn-1-ols in good yields. Sequential treatment of 4-(trimethylsilyl)-2-butyn-1-ols with n-butyllithium, methanesulfonyl chloride, and TBAF furnished the corresponding (3) cumulenes in good yields. (3) Cumulenes with diverse chemical structures were synthesized by selecting different combinations of aldehydes or ketones for condensation with propargylic trimethylsilanes to produce the cumulene precursors. The enyne (3) cumulenes were also synthesized via a similar pathway from 1- (1-(2-alkynyl)cyclopentenyl) -4-trimethylsilyl-2-butyn-1-ols (enediyne alcohols), prepared by condensation of 1-(2-alkynyl-cyclopentenyl)carboxaldehydes (enynyl aldehydes) with 1-lithio-3-trimethylsilyl-1-alkynes. Enyne (3) cumulenes with diverse structures were synthesized. 1,1-Diphenyl allenes were synthesized in good yields via the Horner reaction between an aldehyde or a ketone and 1-(1-lithio-2,2-diphenylethenyl)diphenylphosphine oxide (phosphinoxy carbanion), derived from 1-(1-iodo-2,2-diphenylethenyl)diphenylphosphine oxide and n-butyllithium at {dollar}-78\\sp\\circ{dollar}C. 1,1-Diphenyl-3-(2-alkynyl-1-cyclopentenyl)-1,2-propadienes (enyne-allenes) with two phenyl substituents at the terminus of the allenic end were synthesized in excellent yields by using a phosphinoxy carbanion to react with enynyl aldehydes. Thermolysis (37-80{dollar}\\sp\\circ{dollar}C) of 1,4-cyclohexadiene solutions of the above enyne-allenes gave indan derivatives via {dollar}\\alpha{dollar},3-didehydrotoluene biradicals having a reactive aryl radical center and a stabilized triarylmethyl radical center. In the absence of 1,4-cyclohexadiene, 1,1-diphenyl-3- ( (2-(2-methylphenyl)ethynyl) -1-cyclopentenyl) -1,2-propadiene (enyen-allene) underwent intramolecular H-atom transfer between the proximal benzylic methyl group and the aryl radical center to give the more stable biradical, leading to 7,7-diphenyl-6,7,16,17-tetrahydro-15H-cyclopenta (b) -phenanthrene. (Z)-4-Trimethylsily-1- (2-alkynl-1-cyclopentenyl) -1-buten-3-ynes ((Z,Z)-3,5-octadiene-1,7-diynes) were synthesized by condensation of enynyl aldehydes with an allenyl-borane to furnish (1S,2R)-2-(tert-butyldimethylsilyl)-4-(trimethylsilyl)- (2-alkynyl-1-cyclopentenyl) -3-butyn-1-ols followed by the elimination step of the Peterson olefination reaction. Desilylation of (Z)-4-(trimethylsilyl)-1- (2-(trimethylsilylethynyl)-1-cyclopentenyl) -1-butyn-3-yne with TBAF followed by two consecutive electrocyclizations resulted in the formation of the corresponding benzocyclobutadiene, which dimerized to angular dimers. Treatment of (Z)-1- (2-(1-hexynyl)-1-cyclopentenyl) -4-trimethylsilyl-1-butyn-3-yne with TBAF produced only one angular dimer. On the other hand, the presence of a phenyl substituent on the four-membered ring directed the dimerization of the corresponding benzocyclobutadiene toward the linear dimer, which then underwent a facile thermal rearrangement to dibenzocyclooctadiene. Interestingly, benzocyclo butadienes having an alkenyl substituent on the four-membered ring dimerized via a formal (4+4) cycloaddition to the 1,5-cyclooctadienes.