The preparation and electrocyclic ring-opening of cyclobutenes: Stereocontrolled approaches to substituted conjugated dienes and trienes

Ring Opening Metathesis Polymerization (ROMP) of cis‐ and trans‐3,4‐Bis(acetyloxymethyl)cyclobut‐1‐enes and Synthesis of Block Copolymers

“…cis-Cyclobut-3-ene-1,2-dicarboxylic anhydride (1), [24] cisand trans-3,4-bis(acetyloxymethyl)cyclobutene (2) and (3) were synthesized according to literature procedures. [22] Deuterated solvents were purchased from SDS and used without further purification.…”

“…[24] Starting from 1 cis-3,4-sbis(acetyloxymethyl)cyclobutene (2) and trans-3,4-bis(acetyloxymethyl)cyclobutene (3) were synthesized according to two different procedures already reported in the literature as displayed in Scheme 1. [21,22] As expected, all these cyclobutenes were thermally unstable resulting in the formation of dienes by thermal opening of cyclobutenes, which is a long established route. [25] Polymerization Initial polymerization of monomers 2 and 3 was accomplished with initiators I and II as shown in Scheme 1.…”

“…[15][16][17][18][19][20] Herein, we describe the synthesis and the characterization of substituted poly(cyclobutenes) derived from the stereoisomers cis-3,4-bis(acetyloxymethyl)cyclobutene (2) and trans-3,4-bis(acetyloxymethyl)cyclobutene (3). The previously reported [21,22] stereoisomer 2 and the stereoisomer 3, not yet polymerized, were selected in order to allow a better understanding of the effects of the substituents on the regioselectivity and stability of the propagating species during the ROMP of strained cyclic olefins with the ruthenium initiator systems I and II. The activity of initiators I and II was studied by determination of the rates of propagation and the living synthesis of substituted polybutadienes was confirmed using a sequential monomer addition experiment.…”

Flash vacuum pyrolysis of argentilactone

“…The E,E-isomer 3 is the next most abundant isomer in the essential oil (and, as the most thermodynamically stable isomer, might be expected to predominate at high pyrolysis temperatures). If present, a characteristic multiplet at d H 5.71 (1H, J 14.9 and 7.0 Hz) should be observable [9] but no such signal was present. The other two undecatriene isomers 4 and 6 occur in trace quantities in the essential oil and again no characteristic signals were observed in the proton NMR spectra [1,9,10].…”

“…The undecatriene isomers 2-4 and 6 have been previously described in the literature [8][9][10]. Characteristic signals from their 1 H NMR data sets were used to exclude their presence to any significant extent in the pyrolysate mixtures.…”