2-Chlorobicyclo[2.2.1]hept-5-ene-2-carboxamide and 2-chlorobicyclo[2.2.1]heptane-2-carboxamide as precursors of bicyclo[2.2.1]hept-5-en-2-one and bicyclo[2.2.1]heptan-2-one: resolution, absolute configuration and hydrogen-bonding properties

Rhodium(III)‐Catalyzed Synthesis of Cyclopenta[b]pyrroles from 1,2‐Diketones, 2‐Aminopyridine, and Alkynes

“…These pioneering efforts served to motivate early theoretical9 and experimental10 endeavors, the latter including extensive studies of dispersive and absorptive chiroptical phenomena in the solution phase. Plettner et al 11. have compiled [ α ] D values from several asymmetric syntheses of norbornenone and have assigned the (1 R ,4 R ) absolute configuration to the positive sign of this quantity through crystallographic analyses of a chemical precursor.…”

Asymmetric Total Synthesis of Alkaloids 223A and 6-epi-223A

“…10,11 Swern oxidation of 8 provided the known norbornenone 6 in 92 % yield 12. α-Alkylation of 6 in 4:1 THF/HMPA with 1-chloro-3-iodopropane followed by azide substitution gave the desired ring expansion substrate 13,14.…”

Photocycloaddition of 2,3-Dihydro-2,2-dimethyl-4H-thiopyran-4-one (a 4-Thiacyclohex-2-enone) to bona fide Triplet Quenchers. A Contradiction?

“…A similar experiment wherein 4 is replaced by ethylidenemalononitrile (9) leads to the selective formation of 10, whereas irradiation in the presence of 2,3-dimethylbuta-1,3-diene (11) gives a 1:4:4:1 mixture (by GC as well as by 1 H NMR) of products 12-15 (numbering is by increasing GC retention times) (Scheme 1). Irradiation of 2 in the presence of isoprene (16) affords a more complex mixture of 17-24 (10:30:20:25:5:3:2:5, by 1 H NMR with only three peaks present by GC) (numbering is by decreasing chemical shift of H1), respectively (Scheme 2). In contrast, irradiation of 2 in the presence of 2,5-dimethylhexa-2,4-diene (25) under these conditions does not afford any enonealkene adduct, only dimers of 25 are formed, as monitored by GC.…”

“…in reactions with cyclopentadienes or cyclohexadienes. The resulting achloronitriles represent interesting synthetic intermediates as they can be converted either into chlorobicycloalkenecarboxamides under mild hydrolytic conditions, 16 or, more frequently, into the corresponding ketones by treatment with potassium hydroxide in aqueous dimethyl sulfoxide. 17,18 In contrast, light-induced [2+2] cycloaddition to 4 affording a diastereomeric mixture of 1-chlorocyclobutanecarbonitriles has only been reported for acenaphthene, whose triplet energy (E T ~ 248 kJ/mol) is expectedly low.…”