Convenient One-Step Synthesis of Substituted 1,3-Butadienes from Aldehydes and Ketones

General Synthetic Entry to Linearly-Fused Dihydrobenzocyclobutene-1,2-diones and Benzocyclobutene-1,2-diones via Annulation of 1,2-Bis(methylene)carbocycles with 3-Chloro-3-cyclobutene-1,2-dione1

“…We began by examining the reaction of semisquaric chloride ( 1 ) with the 1,2-bis(methylene)cycloalkanes 2a − c , which were prepared by treatment of the respective 2-methylcycloalkanone with KO- t -Bu following literature procedures . On combining 1 with 1,2-bis(methylene)cyclohexane ( 2a ) in dichloromethane, the solution immediately took on a deep-red color and began to boil gently.…”

A Diels–Alder route to angularly functionalized bicyclic structures

“…Prepared using 11 (76.1 mg, 0.500 mmol) and 1,2-dimethylenecyclohexane18 (270 mg, 2.50 mmol), 27 was isolated as an off-white solid (45.6 mg, 35%) after careful column chromatography. 1 H NMR (CDCl 3 , 400 MHz, 333.15 K) δ 2.79 (d, J = 17.6 Hz, 1H), 2.68 (d of AB pattern, J = 18.8 Hz, 1H), 2.54 (d of AB pattern, J = 18.8 Hz, 1H), 2.31-2.24 (m, 1H), 2.20 (d, J = 18.0 Hz, 1H), 2.10-2.02 (m, 2H), 1.92-1.56 (m, 13H); 13 C NMR (CDCl 3 , 100 MHz, 333.15 K) δ 124.2, 123.1, 121.5, 90.4, 39.7, 39.4, 36.1, 34.0, 32.8, 29.7, 29.5, 29.3, 22.6, 22.1, 21.0; IR (KBr) 2930, 2236, 1789, 1546, 1439, 851 cm −1 ; HRMS (EI) exact mass calculated for [M+1] + (C 15 H 21 N 2 O 2 ) required m / z 261.1603, found m / z 261.1607.…”

Synthetic methodologies for carbo-substituted conjugated dienes

“…In the case of cyclopropyl(alkenyl)methanols 556, conjugated diene system 557 is produced. 486 ± 488 A very simple method for the synthesis of dienes consists in heating of aliphatic a-branched ketones 558 in DMSO with potassium tert-butoxide, 489 DMSO serving as the source of a new carbon atom in the molecule of product 559. Unfortunately, in many instances, these reactions give mixtures of isomers.…”