932108-32-2Relevant academic research and scientific papers
Synthesis of α,β-unsaturated α′-haloketones through the chemoselective addition of halomethyllithiums to Weinreb amides
Pace, Vittorio,Castoldi, Laura,Holzer, Wolfgang
, p. 7764 - 7770 (2013/09/02)
A straightforward synthesis of variously functionalized α,β-unsaturated α′-haloketones has been achieved through the chemoselective addition of halomethyllithium carbenoids to Weinreb amides at -78 C. A comparative study employing the corresponding esters under the same reaction conditions pointed out that the instability of the tetrahedral intermediate formed from the latter is responsible for the observed formation of carbinols instead of the desired haloketones.
Diels-Alder reactions of 4-alkenylthiazoles: A new approach to thiazole functionalization
Alajarin, Mateo,Cabrera, Jose,Pastor, Aurelia,Sanchez-Andrada, Pilar,Bautista, Delia
, p. 2097 - 2105 (2007/10/03)
Somewhat unexpectedly, the computed highest occupied molecular orbital (HOMO) energies of some 4-alkenylthiazoles afforded values close to those calculated for the Danishefsky-Kitahara and Rawal dienes. In fact, 4-alkenylthiazoles behave as all-carbon die
On the [2+2] cycloaddition of 2-aminothiazoles and dimethyl acetylenedicarboxylate. Experimental and computational evidence of a thermal disrotatory ring opening of fused cyclobutenes
Alajarin, Mateo,Cabrera, Jose,Pastor, Aurelia,Sanchez-Andrada, Pilar,Bautista, Delia
, p. 5328 - 5339 (2007/10/03)
The reaction of 2-(phenylamino)- and 2-(dimethylamino)thiazoles with dimethyl acetylenedicarboxylate led unexpectedly to dimethyl 6-(phenylamino)- and 6-(dimethylamino)-3,4-pyridinedicarboxylates. Those compounds reasonably result from a sequence of reactions initiated by a [2 + 2] cycloaddition of the alkyne to the formal C=C of the thiazole ring. These pyridines were obtained in nearly all the cases assayed as the exclusive reaction products under rather mild conditions and in fair to good yields. In contrast, the regioisomeric 2-amino-3,4-pyridinedicarboxylates, which would result from a [4 + 2] cycloaddition followed by sulfur extrusion, were only obtained in one particular case. The two reaction paths leading alternatively to both regioisomers were investigated computationally. The respective [2 + 2] and [4 + 2] cycloadducts were found to be formed stepwise from a common dipolar intermediate. Notably, the step following the [2 + 2] cycloaddition (i.e., the ring opening of the fused cyclobutene intermediate to give an all-cis 1,3-thiazepine) was found to take place in a disrotatory mode. Although geometric constraints and electronic factors may reduce the energy for the disrotation, the implication of the fused five-membered ring in the electronic reorganization leading to the 1,3-thiazepine is determinant. In this sense, this step could be regarded also as a thermally allowed six-electron five-center disrotatory electrocyclic ring opening. The proposed mechanism was experimentally supported by the isolation of several intermediates and other experimental facts.
