v. Braun, Julius published the artcileTransformations of cyclopentadiene, Application of (2-Bromoethyl)cyclopentane, the publication is Berichte der Deutschen Chemischen Gesellschaft [Abteilung] B: Abhandlungen (1937), 1750-60, database is CAplus.
It had been found (C. A. 22, 1146) that 2-cyclopentyl chloride (I) reacts like allyl chloride with aromatic Grignard reagents and the resulting arylcyclopentenes take up HBr to form 2-arylcyclopentyl bromides As was expected, nonaromatic Grignard reagents act in the same way with I and addition of HBr to the products offers no difficulty but, contrary to the aromatic compounds, it results in the formation of 3-alkylcyclopentyl bromides. Their structure was proved by the reaction recently described (C. A. 28, 2329.3): replacement of the Br by CO2H by means of Mg and CO2, α-bromination of the acid, and conversion of the Br acid into the acid chloride which with NaN3 gave a 3-alkylcyclopentanone. HBr thus adds to the alkylcyclopentenes in just the opposite way to its addition to the aryl compounds O and halogens, like Ph, attract electrons but their effect decreases rapidly with distance and, as was expected, β-2-cyclopentenylethyl alc. (II) heated with HBr gave, together with some of the unsaturated bromide (III), the saturated β-(3-bromocyclopentyl) ethyl bromide (IV). It was attempted to prove the structure of IV by replacing both Br atoms with CO2H but the dicarboxylic acid could not be obtained pure. That, however, it was not the 2-Br compound was indicated by the fact that with 1 mol. malonic ester and 2 atoms Na it gave, along with high-mol. compounds, and a brominated ester of lower mol. weight, only a small amount (30%) of a compound C14H22O2 (V). Had the ring-substituted Br in IV been in the 2-position, the strainless bicyclo (0.3.3)octane derivative would undoubtedly have been formed very smoothly. V is believed to be the bicyclo (1,2,3) octane It is decarboxylated to the monocarboxylic acid (VI) by means of which it is hoped to develop the field of these bicyclo compounds, representatives of which (with the exception of the Komppa ketone) are as yet known only in a few complex derivatives of the camphor series. Thus far it has not been possible to pass from IV to the parent hydrocarbon of the bicyclo(1.2.2.)heptane series; as was to be expected from the strain existing in the latter system, the action of Na on IV is exclusively extramol. and there results a mixture, boiling within wide limits, of hydrocarbons (C7H12)n of varying mol. weight 2-Ethylcyclopentene (VII) (30% yield), b768 99-103°, d420 0.7874, nD20 1.43030. It readily adds Br in CS2 to form a liquid dibromide, b12 98-100°, faintly yellow but soon decomposing and darkening. 3-Bromo-1-ethylcyclopentane (65% from VII shaken 50 hrs. with 2-3 volumes fuming HBr), b42 84-6°, d420 1.2597. It reacts readily with Mg and when the product is treated with CO2 and worked up in the usual way it gives the Na2CO3-insoluble 3,3′-diethylbicyclopentyl, b15 125°, d415 0.8757, nD20 1.47097, and the Na2CO3-soluble 3-ethylcyclopentanecarboxylic acid, b15 132-4°, whose acid chloride, b11 176-8°, with 1 mol. Br at 125° gives almost quantitatively the α-Br derivative, b11 110°, and this, in pyridine solution or suspension, heated with NaN3, then treated with alc. and alkali, acidified with HCl after 15 min. and distilled with steam, yields 3-ethylcyclopentanone, b. 150°, forming a semicarbazone, m. 175°, and with m-O2NC6H4CHO, alc. and a trace of alkali, a lemon-yellow condensation product, C20H18O5N2, m. 142°. 2-Isoamylcyclopenten (60%), b59 86-7°, does not darken on standing, d422 0.7969. 3-Bromo-1-isoamylcyclopentane, b15 109-10°; 3-carboxylic acid, b20 160°, d420.5 0.9566. 2-Dodecylcyclopentene (50%), b15 172°, d416 0.8262, nD20 1.45667. Addition of HBr requires long heating, a considerable part of the hydrocarbon remaining unattacked even after 15 hrs. The 3-bromo-1-dodecylcyclopentane b0.1 163°, d414.5 0.9811. Mg and CO2 give, with some 3-carboxylic acid, m. 29°, chiefly dodecylcyclopentane, b15 175°, d418 0.8280, nD20 1.45737 and 3,3′-didodecylbicyclopentyl, b0.2 260° (the latter is a semi-solid thick oil, probably consisting of a mixture of stereoisomers). The cyclopentene forms a dibromide, b0.2 180° without appreciable decomposition but becomes discolored on standing. C5H9MgCl and I react very vigorously, yielding somewhat more than 60% 2-cyclopentenylcyclopentane, b9 60-4°, d420 0.8838; shaken 60 hrs. with fuming HBr, it gives almost 80% 3-bromobicyclopentyl, b9 115°, which with Mg and CO2 yields bicyclopentyl, b9 67°, almost pure tetracyclopentyl, (C5H9C5H8–)2, b9 205-7°, and about 30% bicyclopentyl-3-carboxylic acid, b13 172°, d419 1.0398; acid chloride, b10 125°, gives 70% of the α-Br derivative, faintly yellow, b0.3 128-32°, which with NaN3 yields 3-cyclopentylcyclopentanone, volatile with steam (oxime, b10 145-6°, m. 46°; semicarbazone, m. 184°; bis(m-nitro-benzal) derivative, yellow-red, m. 172°). 2-Cyclopentenyl-cyclohexane (60%), b12 80-5°, d418 0.8995, nD20 1.48698. 3-Bromo-l-cyclohexylcyclopentane (70%), b11 132-6°, becomes yellowish and splits off a little HBr on standing; Mg and CO2 give cyclopentylcyclohexane, b11 86-8°, d423 0.8886, nD20 1.47491, 15% 3,3′-dicyclohexylbicyclopentyl, b0.1 180°, d418 0.9592, nD20 1.51290, and about 15% 3-cyclohexylcyclopentanecarboxylic acid, b11 180°, d417 1.0343, nD20 1.49255; the acid chloride, b11 142-4°, gives an α-Br derivative, b0.05 140-2°, which with NaN3 yields 3-cyclo-hexylcyclopentanone, b10 126°, d419 0.9730, nD20 1.48476 (semicarbazone, m. 186°; bis(m-nitrobenzal) derivative, orange, m. 122°). Et 2-cyclopentenylacetate, from the acid heated 3 hrs. on the water bath with 2 parts by weight of EtOH and 0.1 part concentrated H2SO4, b12 81°. With 10 atoms Na in EtOH it gives 70% II, b15 82-3°, d423.5 0.9432, nD25 1.4695, vigorously decolorizes KMnO4, readily takes up 2 H atoms with Pd to give β-cyclopentylethyl alc. (also obtained from C5H9CH2CO2Et with Na and alc.), bit 84-5°,which with HBr at 100° gives almost 100% of the bromide, C5H9CH2CH2Br, b11 70-1°. The fraction b0.4 below 100° (chiefly around 70°) of the product of the reaction of II with HBr and which consists chiefly of III with unchanged II, gives with NHMe2 in benzene at 100° the unsaturated base, C5H7CH2CH2NMe2, b13 66-8°, d421 0.8291 (picrate, m. 136-8°; chloroplatinate, m. 148°; methiodide, m. 223°). IV, b0.4 100°, darkens only on long standing. V, b12 155-60°; free dicarboxylic acid, powder, m. 189-90° (foaming) with formation of VI, b13 150-2°, d426 1.0603.
Berichte der Deutschen Chemischen Gesellschaft [Abteilung] B: Abhandlungen published new progress about 18928-94-4. 18928-94-4 belongs to bromides-buliding-blocks, auxiliary class Bromide,Aliphatic cyclic hydrocarbon, name is (2-Bromoethyl)cyclopentane, and the molecular formula is C16H14O6, Application of (2-Bromoethyl)cyclopentane.
Referemce:
https://en.wikipedia.org/wiki/Bromide,
bromide – Wiktionary