The Synthesis, Purification and Properties of Some Polyalkylcyclopropanes: Reduction of α,γ-Dibromides¹

Stereoselective 1,3-debromination reactions

“…isomer 2a (860 mg, crystallized from hexane), mp 63-64"C, and the meso isomer 2b (220 mg, crystallized from hexane), mp 53-54°C. Isolatiot~ of lactone 5 Treatment of (*)-2,4-dibromoglutaric acid with one equivalent of (-)-brucine ((-)-cinchonidine or (+)-cinchonine led to similar results) in acetone solution led to a gummy precipitate of brucine. HBr.…”

Cyclopropanation with Dimethylcarbene

“…When, on the other hand, the reaction temperature is lowered from -30" to -70" C, the yield of (4) increases to almost 50% (further reduction giving no further improvement). A11 further experiments to optimize the cyclopropanation conditions were therefore carried out at Since in all experiments 35-45% of (3) was recovered unchanged['*], the olefin fraction was halved; the yield of (4), relative to the amount of (3) consumed, however, remained unchanged. Identical yields of (4) (45-50%) were also obtained on doubling the butyllithium fraction or on using a fourfold excess of olefin.…”

“…2-Substituted butadienes could be formed by electrophilic attack on this species. Indeed, the 2-substituted butadieneiron complexes (2) and (3). which were isolated as air stable compounds in 80 and 45% yields, respectively, are formed directly from butatriene(hexacarbony1)diiron (1) The organic ligand of complex (1) is not only acylated but also hydrogenated.…”

“…With n-butyllithium at -3O"C, the cycloadduct (4) could indeed be isolated, apart from unchanged (3); the yield was about 2OYo with respect to the olefin consumed in the reaction. On the other hand, when methyl-or isopropyllithium were employed as metalating agents, at best traces of (4) could be detected by gas chromatography (GC) or GC/MS.…”

Stereochemistry of the reductive debromination of (R)-meso- and (S)-meso-3-methyl-2,4-dibromopentane

“…By the same procedure used for the preparation 5, 4.89 g (37.56 mmol) of (R)-meso-4,5,6trimethyl-l,3-dioxane and 3.51 g of p-toluenesulfonic acid in 24 mL of methanol for 120 h y ielded 3.63 g (82%) of crude oil (solvent removed but product not distilled). The NMR spectrum indicated that the oil was sufficiently pure 6 to use without further purification: NMR b 0.83 (d, J = 6 Hz, 3 ), 1.08 (d, J = 6 Hz, 7 H, hides 1 H multiplet), 3.82 (m, 2 ), 4.21 (variable, s, 2 H) [lit.11 NMR b 0.88 (d, J = 6.5 Hz, 3 ), 1.16 (d, J = 6.5 Hz, 7 H, hides 1 H multiplet), 4.03 (m, 2 H)[. (R) -meso-3-Methyl-2,4-dibromopentane (3).…”