NHC-catalyzed β-specific addition of N-based nucleophiles to allenoates

Abstract

N-heterocyclic carbene (NHC) catalyzed reactions of nitrogenous heterocycles or trifluoromethylated acylhydrazone with allenoates gave regiospecific β-adducts. DFT calculations rationalized the origination of regio- and E/Z selectivities.

Tandem Addition/Cyclization/Halogenation Reaction of Difluoromethylated N-Acylhydrazones with Allyltrimethylsilanes

“…Substrates 1a−1u were prepared according to the literature (see ESI for details). 25 Substrates 2c−2f were prepared according to the literature (see ESI for details). 26 General Procedure for the Synthesis of Products 4 and 6.…”

“…Purified by column chromatography (EA/petroleum ether, 1:8, R f = 0.5); colorless oily liquid (68 mg, 70%); 1 H NMR (400 MHz, CDCl 3 ): δ 6.38 (t, J = 54.0 Hz,1H),1H),3.87 (dd,J = 10.4,5.6 Hz,1H),3.56 (dd,J = 10.4,2.4 Hz,1H),1H),2H),1.89 (d,J = 11.2 Hz,1H),4H),2H), 1.38−1.17 (m, 3H); 13 C{ 1 H} NMR (150 MHz, CDCl 3 ): δ 175.7, 149.1 (t, J C−F = 31.8 Hz), 110.6 (d, J C−F = 232. 8 Hz),56.8,41.5,34.0,34.0,29.1,28.2,25.7,25.6,25. (5-(Bromomethyl) (phenyl) methanone (6i). Purified by column chromatography (EA/petroleum ether, 1:10, R f = 0.6); yellow oily liquid (85 mg, 72%); 1 H NMR (400 MHz, CDCl 3 ): δ 7.78 (d, J = 7.0 Hz, 2H), 1H),4H),3H),6.37 (t,J = 54.0 Hz,1H),4.96 (d,J = 10.8 Hz,1H),4.21 (d,J = 10.8 Hz,1H),3.72 (d,J = 18.4 Hz,1H),3.27 (d,J = 18.4 Hz,1H); 13 C{ 1 H} NMR (150 MHz, CDCl 3 ): δ 167.8, 148.2 (t, J C−F = 31.…”

“…Purified by column chromatography (EA/petroleum ether, 1:8, R f = 0.5); colorless oily liquid (68 mg, 70%); 1 H NMR (400 MHz, CDCl 3 ): δ 6.38 (t, J = 54.0 Hz, 1H), 4.86−4.80 (m, 1H), 3.87 (dd,J = 10.4,5.6 Hz,1H),3.56 (dd,J = 10.4,2.4 Hz,1H),1H),2H),1.89 (d,J = 11.2 Hz,1H),4H),2H), 1.38−1.17 (m, 3H); 13 C{ 1 H} NMR (150 MHz, CDCl 3 ): δ 175.7, 149.1 (t, J C−F = 31.8 Hz), 110.6 (d, J C−F = 232. 8 Hz),56.8,41.5,34.0,34.0,29.1,28.2,25.7,25.6,25.…”

Regioselective Hydrothiolation of Allenoates through a Ca(OTf)2‐Promoted Three‐Component Reaction

“…For instance, nucleophilic addition to unsaturated precursors such as alkynes and allenes is one of the most straightforward and practical ways to obtain these compounds [1] . In this context, using phosphines, [2] NHCs, [3] or metals like rhodium [4] proves that controlling the regioselectivity of nucleophilic addition to allenic scaffolds highly depends on the kind of catalyst (Scheme 1a).…”