‘Push–Pull’ and spirobicyclic structures by reacting N-methyl cyclic ketene-N,X (X=S, O)-acetals with isocyanates and isothiocyanates

Push–pull alkenes by reacting N,N′-dimethyl cyclic ketene N,N′-acetals with isocyanates: synthesis, structures, and reactivities

“…[9][10][11] These special properties provided impetus for the synthesis, characterization, and applications of push-pull alkenes 12-24 along with theoretical investigations to understand and predict these effects. [25][26][27][28][29][30][31] Recently, Pittman's group 32,33 reported the reactions of cyclic ketene-N,X-acetals (X = O, S) with isocyanates and isothiocyanates to generate push-pull alkenes in excellent yields. In this Letter, the conversion of cyclic ketene-N,N-acetals 2 and 3 to sterically crowded push-pull alkenes via reactions with isocyanates will be demonstrated and discussed for the first time.…”

“…4), was also synthesized according to a literature method. 32,33 The crystal structure of 14 was determined in order to compare with those of 11d, 11a, and 13a. The length of the central C6-C7 double bond in crystals of 14 (1.39 Å) is considerably shorter than those in 10d (1.45 Å), 11a (1.47 Å), and 13a (1.47 Å).…”

Four-membered ring cyclic ketene –O,O–, –O,S–, –O,N–, –S,S–, –S,N–, and –N,N–acetals and their corresponding cations: a computational study

“…Pittman and coworkers have extensively explored the synthetic potential of many cyclic ketene acetal species [1,2] with both mono-and dielectrophiles, discovering a rich variety of reactions ranging from tandem cyclizations [1,3,4], bis additions followed by ring-opening and re-closure isomerizations [2], arylvinyl ester formation [1,4,5], ''push-pull'' compound formation [6,7], new heterocyclic ring and fused ring formation [2,3,6,8,9], ring-opening reactions [10], ring-retained polymerization and copolymerizations [11][12][13][14][15][16][17][18][19][20], spirobicyclic ring formation [21], and stereoselective radical cyclizations [21,22]. However, all of these studies have been carried out only on five-; six-; and seven-membered ring systems .…”

Theoretical studies of five-membered ring ketene acetals

“…Such reactivity has been exploited in the synthesis of heterocyclic systems, spirobicyclic ring systems, and pushpull olefins [10][11][12]. Stereo-controlled radical cyclizations onto the methylene carbon have also been reported [13,14].…”