Di-n-propyl formal

Poly (2-butyne-l,4-dioxymethylene). From Di-m-propyl Formal. A three-necked, round-bottomed flask, fitted with a gas inlet tube, a mechanical stirrer, and a graduated Dean-Stark moisture trap with a condenser attached, was charged with 66 grams of di-n-propyl formal, 45... 

Another type of dimerization was observed by Japanese authors198. In the presence of Ni°, compounds like bis(l,5-cyclooctadiene) nickel(0), diphenyl and di-n-propyl cyclopropenone, and cyclohepteno cyclopropenone are transformed to tetra-substituted p-benzoquinones (261/262) by formal (2 + 2) or (3 + 3) cycloaddition of two cyclopropenone moieties effected by metal complexing. 

Formally this corresponds to the [1,5] sigmatropic migration of the di-n-propylboryl group. However, it has been supposed that this dynamic behavior is instead caused by two consequent [1,3]-B migrations with the intermediacy of relatively unstable isomer 20a (Scheme 2.19). This conclusion was supported by the close values of the activation barriers of borotropic migrations in 20 (found from 2D EXSY NMR) and structurally similar Z-2,4-pentadienyl(di-n-propyl)borane 16b (see Table 2.1). 

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