Synthetic investigations on the chemistry of polyene compounds. LVI. Synthesis of (all-E)-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethylnona-2,4,6,8-tetraenoic acid

Microwave-Mediated Claisen Rearrangement Followed by Phenol Oxidation: A Simple Route to Naturally Occurring 1,4-Benzoquinones. The First Syntheses of Verapliquinones A and B and Panicein A

“…The route to panicein A is similar in its requirement for a tertiary allyl ether substrate for the Claisen rearrangement. The starting material is the propargylic alcohol, 5-(4-methoxy-2,3,6-trimethylphenyl)-3-methylpentyn-3-ol ( 17 ), prepared by addition of ethynylmagnesium bromide to the known ketone 4-(4-methoxy-2,3,6-trimethylphenyl)butan-2-one, obtained in four steps from 2,3,5-trimethylphenol . In this instance, copper(II)-catalyzed coupling of the tertiary trifluoroacetate to a phenol gave poor yields, so a modification using a propargylic carbonate was used .…”

A Modular Approach for the Synthesis of Natural and Artificial Terpenoids

“…To further demonstrate the generality and versatility of this chem-stamp, five typical terpenoids with isoprene unit(s) were synthesized in a modular fashion just from different readily available starting aldehydes 21, 32, 36, and 41, or aryl boronate 27 (Scheme 3). 1) Acitretin [17] 26 was synthesized from commercially available 4-methoxy-2,3,6-trimethylbenzaldehyde 21. Two rounds of applying this chem-stamp gave polyenyl aldehyde 25.…”

“…[13] On the other hand, the artificial creation of isoprene unit in such terpenoids I heavily relies on cross-coupling reactions creating CÀ C single bond between two CÀ C double bonds, and Wittig or Horner-Wadsworth-Emmons (HWE) reactions generating CÀ C double bonds, [4,14] requiring the multistep synthesis of suitable precursors (Scheme 1c). For the terpenoids with two isoprene units, such as retinal, [4] vitamin A acetate, [4,15,16] acitretin, [17] and fenretinide, [4,18] each isoprene unit has been constructed separately by different methods, generally lacking efficiency. Thus, efficient methods to overturn these known protocols for the modular construction of the library with diversified such compounds are of high interest both for synthetic and medicinal chemists.…”

Total synthesis of panicein A2

“…Firstly, aldehyde 10 was required; it was prepared through methylation followed by Vilsmeier–Haack reaction of 2,3,5-trimethylphenol ( 11 ), giving 10 in 51% yield over two steps ( Scheme 1 ) [ 7 ]. Aldehyde 10 then underwent an aldol reaction according to the procedures of Samokhvalov et al to provide ketone 12 in 66% yield [ 8 ]. The selective reduction of the olefin in α,β-unsaturated ketone 12 was then attempted using the Raney nickel catalyst under hydrogen as previously reported [ 8 ]; unfortunately no product 13 was formed.…”

“…Aldehyde 10 then underwent an aldol reaction according to the procedures of Samokhvalov et al to provide ketone 12 in 66% yield [ 8 ]. The selective reduction of the olefin in α,β-unsaturated ketone 12 was then attempted using the Raney nickel catalyst under hydrogen as previously reported [ 8 ]; unfortunately no product 13 was formed. Following this, a range of conditions were employed to reduce the double bond in the presence of the α,β-unsaturated ketone, including Pd/C and H 2 , NaBH 4 and Pd/C in the presence of acetic acid [ 9 ], and NaBH 4 with CoCl 2 [ 10 ]; all of these reductive conditions gave complex, inseparable mixtures of overreduction products of the ketone functionality.…”