One-Pot Regioselective Synthesis of meta-Terphenyls via [3 + 3] Annulation of Nitroallylic Acetates with Alkylidenemalononitriles

Abstract

A highly efficient one-pot method has been developed for the synthesis of meta-terphenyls via a regioselective [3 + 3] annulation-elimination sequence involving Morita-Baylis-Hillman (MBH) acetates of nitroalkenes and alkylidenemalononitriles. The reaction takes place in a regioselective manner under mild conditions (Et3N, room temperature) to afford a wide variety of meta-terphenyls bearing aryl, heteroaryl and styrenyl groups. This novel [3 + 3] annulation takes advantage of the 1,3-bielectrophilic character of MBH acetates and 1,3-binucleophilic character of alkylidenemalononitriles and proceeds in a cascade fashion comprising an SN2' substitution, intramolecular 6-endo-trig Michael addition and double elimination. Representative synthetic transformations of the products, for instance, to meta-terphenyl derived isoindolinones have also been demonstrated.

Site‐Specific S‐Allylation of α‐Enolic Dithioesters with Morita‐Baylis‐Hillman Acetates at Room Temperature: Precursor for Thiopyrans

“…Motivated by the above observations (Table 1, entries [11][12][13][14][15], we decided to carry out the reaction of pure isolated compound 3 a under ethanol reflux. Thus, when compound 3 a was subjected to ethanol reflux for 10 h, a mixture of 3 a and 5 a (3 a:5 a = 42:58) was obtained via thio-Claisen rearrangement (Scheme 2).…”

“…All the chemicals and reagents except αenolic dithioesters and MBH acetates were commercially available and used as received. α-Enolic dithioesters (1) [17,18] and MBH acetates (2) [12,15] were prepared following the literature procedures. Thin-layer chromatography (TLC) was performed using silica gel 60 F 254 precoated plates.…”

“…5-methyl-1-(methylthio)-3-oxohex-1-en-1-yl 5, 195.3, 167.2, 167.0, 161.5, 161.0, 143.9, 143.7, 134.5, 134.2, 129.8, 129.7, 129.7, 129.4, 129.1, 128.8, 126.0, 124.9, 114.7, 113.6, 52.6, 52.4, 52.2, 32.3, 29.4, 25.6, 25.5, 22.8, 22.7, 17.5, 15. -(((1-(isobutylthio)-3-oxo-3-(thiophen-2-yl) prop-1en-1-yl)thio)methyl)-3-phenylacrylate (3 n): (Mixture of Eand Z-isomers), Sticky yellow solid, yield 87% (376 mg); 1 H NMR (500 MHz, CDCl 3 ) δ 9. 12,9.04 (s,1H),8.70,8.68 (d,J = 4.0 Hz,1H),8.22,8.15 (d,J = 8.0 Hz,1H),7.97,7.92 (s,1H),6H),6.81,6.77 (s,1H),4.30,4.22 (s,2H),3.89,3.84 (s,3H), 2.99, 2.94 (d, J = 8.0 Hz, 2H), 2.06, 1.99 (m, 1H), 1.10, 1.07 (d, J = 6.5 Hz, 6H); 13 C NMR (125 MHz, CDCl 3 ) δ 183. 8, 183.5, 167.4, 167.1, 167.0, 166.7, 152.2, 152.2, 149.0, 148.9, 144.5, 144.0, 135.5, 135.4, 134.5, 134.5, 134.1, 129.9, 129.7, 129.6, 129.5, 129.1, 128.8, 125.8, 124.5, 123.7, 123.5, 110.6, 109.6, 52.7, 52.5, 43.3, 40.3, 32.9, 30.0, 28.6, 27.4, 22.3, 22.2.…”

“…The MBH adducts have the advantages of good tolerance to many functional groups, excellent regioselectivity, and good to excellent yields. The MBH acetate is one of the most potent synthons, which have been systematically and meticulously employed in numerous synthetic transformations [12] as well as in allylation chemistry. [13] A range of CÀ C and C-heteroatom bonds have been formed via the allylation of suitable substrates with racemic MBH acetates as electrophilic allylic precursors.…”

Solventless Synthesis of Quaterphenyls and Terphenyls from Chalcones and Allylsulfones under Phase Transfer Catalysis Conditions

“…However, this approach suffers from the need for additional steps to prepare reactants and the formation of toxic HCN during annulation [15]. On the other hand, a mixture of meta-terphenyl 6a along with sulfonyl-meta-terphenyl 8a has been obtained by reacting allylsulfone 4a with chalcone 5a in the presence of excess of NaH in THF at 50 °C (Scheme 3) [16].…”