Copolymerization of aryldiazomethanes

Abstract

Several aryldiazoalkanes (M2) have been copolymerized with phenyldiazomethane (M1) in toluene‐methanol solution at 40°C, namely, the p‐chloro‐, p‐methoxy‐, p‐mesyl‐o and ‐p‐methyl‐, 2,4‐ and 3,4‐dichlorophenyldiazoalkanes, and the α‐ and β‐ naphthyl‐diazoalkanes. The copolymerization parameters r1 and r2 have been evaluated. By plotting 1/r1 against the Hammett σ values a negative ρ values was found equal to −0.88. From cationic copolymerizations carried out at −78°C in the presence of boron trifluoride‐diethyl ether as catalyst a similar plot of 1/r1 against σ gives a value of ρ equal to −0.82. The negative sign and the agreement between these ρ values demonstrates the cationie mechanism of the methanol polymerization and copolymerization of aryldiazoalkanes.

C1 polymerisation and related C–C bond forming ‘carbeneinsertion’ reactions

“…29 BF 3 mediated polymerisation of aryldiazoalkanes also allows the formation of copolymers from different aryldiazoalkanes (C), but yields and molecular weights are still low (Scheme 3). 30 Recently, boron mediated polymerisation of diazoalkanes was applied to construct polymeric structures based on paracyclophanes that give rise to enhanced p-p stacking (D). 31 Racemic as well as chiral 4-diazomethyl[2.2]paracyclophanes were polymerised with BF 3 ÁEt 2 O resulting in low molecular weight polymers/oligomers in low yields (Table 1, entry 7; rac: M n = 1100 Da, yield = 20%, R p : M n = 1200 Da, yield = 20%, S p : M n = 1300 Da, yield = 13%).…”

Carbohydrate chiral-pool approach to four enantiomerically pure 2-naphthylmethyl 3-hydroxy-2-methylbutanoates

“…TLC of these mixtures showed a strong fluorescent spot of the formate 19 (major) and a more polar 2naphthylmethyl (3R)-hydroxy-(2R)-methylbutanoate 20 (minor), accompanied by UV absorbing compounds having R f s values similar to those of 19. The presence of these impurities was not surprising since it is known that in situ generated aryl diazomethanes are in general not more than 85% pure, 39 and also the transient naphthylmethyl carbenes can decompose to form by-products. It should be pointed out that tagging of the organic acids with fluorescent 1-napthylmethyl or 1-napthylethyl groups was applied to facilitate their detections during HPLC analysis.…”

C1 Polymerization of Fluorinated Aryl Diazomethanes

“…We envisioned the use of a “C1 polymerization” to meet the aforementioned challenge. C1 polymerizations grow polymer chains in single carbon increments , and, as such, afford access to highly substituted polymers. − For example, as shown in Scheme , Ray and Matthies independently demonstrated that various catalysts can be used to convert diazoethane to poly­(methyl methylene). Although the corresponding C1 polymerization reactions were uncontrolled, the polymers produced feature a methyl group on every carbon atom of their backbones. , Since those early reports, emphasis has focused on the use of diazoesters as monomers in part because such compound are relatively stable and can be readily modified through variation of the pendant ester group. ,,,− ,− Fluorinated diazoesters, such as 3,3,4,4,5,5,6,6,6-nonafluorohexyl diazoacetate, 2-fluorophenyl diazoacetate, and 2,6-difluorophenyl diazoacetate, have been subjected to C1 polymerization strategies; however, the products obtained from these reactions are insoluble, which has thwarted characterization and utilization.…”

“…With the monomers in hand, efforts were directed toward using BF 3 ·OEt 2 to induce polymerization; key results are summarized in Table . ,,, A solution of 1a ([ 1a ] 0 = 0.48 M) was first treated with catalytic amounts of BF 3 ·OEt 2 ([ 1a ] 0 /[BF 3 ·OEt 2 ] 0 = 100) at room temperature. While no chemical reaction was evident when the polymerization was performed in diethyl ether, a vigorous evolution of a gas, presumably nitrogen, was observed when benzene or toluene was used as the solvent.…”