936724-58-2Relevant academic research and scientific papers
A Palladium(II)-Catalyzed C-H Activation Cascade Sequence for Polyheterocycle Formation
Cooper, Stephen P.,Booker-Milburn, Kevin I.
, p. 6496 - 6500 (2015/06/02)
Polyheterocycles are found in many natural products and are useful moieties in functional materials and drug design. As part of a program towards the synthesis of Stemona alkaloids, a novel palladium(II)-catalyzed C-H activation strategy for the construction of such systems has been developed. Starting from simple 1,3-dienyl-substituted heterocycles, a large range of polycyclic systems containing pyrrole, indole, furan and thiophene moieties can be synthesized in a single step. Don't overdo it: A palladium(II)-catalyzed C-H activation cascade sequence for the synthesis of polyheterocycles is reported. Aromatization of the initially formed dihydro species occurred with a quinone oxidant. In some cases the use of one equivalent of the oxidant enabled isolation of the dihydro species as a single isomer (see scheme; X=NMe, O, S).
Intramolecular cyclopropanation of unsaturated terminal epoxides and chlorohydrins
Hodgson, David M.,Ying, Kit Chung,Nuzzo, Irene,Freixas, Gloria,Kulikiewicz, Krystyna K.,Cleator, Ed,Paris, Jean-Marc
, p. 4456 - 4462 (2008/02/02)
Lithium 2,2,6,6-tetramethylpiperidide (LTMP)-induced intramolecular cyclopropanation of unsaturated terminal epoxides provides an efficient and completely stereoselective entry to bicyclo[3.1.0]hexan-2-ols and bicyclo[4.1.0]heptan-2-ols. Further elaboration of C-5 and C-6 stannyl-substituted bicyclo[3.1.0]-hexan-2-ols via Sn-Li exchange/electrophile trapping or Stille coupling generates a range of substituted bicyclic cyclopropanes. An alternative straightforward cyclopropanation protocol using a catalytic amount of 2,2,6,6-tetramethylpiperidine (TMP) allows for a convenient (1 g-7.5 kg) synthesis of bicyclo[3.1.0]-hexan-2-ol and other bicyclic adducts. The synthetic utility of this chemistry has been demonstrated in a concise asymmetric synthesis of (+)-β-cuparenone. The related unsaturated chlorohydrins also undergo intramolecular cyclopropanation via in situ epoxide formation.
