Ruthenium porphyrin catalyzed tandem sulfonium/ammonium ylide formation and [2,3]-sigmatropic rearrangement. A concise synthesis of (+/-)-platynecine.
meso-Tetrakis(p-tolyl)porphyrinatoruthenium(II) carbonyl, [Ru(II)(TTP)(CO)], can effect intermolecular sulfonium and ammonium ylide formation by catalytic decomposition of diazo compounds such as ethyl diazoacetate (EDA) in the presence of allyl sulfides and amines. Exclusive formation of [2,3]-sigmatropic rearrangement products (70-80% yields) was observed without [1,2]-rearrangement products being detected. The Ru-catalyzed reaction of EDA with disubstituted allyl sulfides such as crotyl sulfide produced an equimolar mixture of anti- and syn-2-(ethylthio)-3-methyl-4-pentenoic acid ethyl ester. The analogous "EDA + N,N-dimethylcrotylamine" reaction afforded a mixture of anti- and syn-2-(N,N-dimethylamino)-3-methyl-4-pentenoic acid ethyl esters with a diastereoselectivity of 3:1. The observed catalytic activity of [Ru(II)(TTP)(CO)] for the ylide [2,3]-sigmatropic rearrangement is comparable to the reported examples involving [Rh(2)(CH(3)CO(2))(4)] and [Cu(acac)(2)] as catalyst. Similarly, cyclic sulfonium and ammonium ylides can be produced by intramolecular reaction of a diazo group tethered to allyl sulfides and amines under the [Ru(II)(TTP)(CO)]-catalyzed reaction conditions. The subsequent [2,3]-sigmatropic rearrangement of the cyclic ylides furnished 2-allyl-substituted sulfur and nitrogen heterocycles in good yields (>90%). By employing [Ru(II)(TTP)(CO)] as catalyst, the cyclic ammonium ylide [2,3]-sigmatropic rearrangement reaction was successfully applied for the total synthesis of (+/-)-platynecine starting from cis-2-butenediol.
Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam Road, Hong Kong.
Cong-Ying
CY
Zhou
Wing-Yiu
WY
Yu
Philip Wai Hong
PW
Chan
Chi-Ming
CM
Che
D002384:Catalysis; D006574:Heterocyclic Compounds, 2-Ring / Q000138:chemical synthesis*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000138:chemical synthesis*; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism; D013452:Sulfonium Compounds / Q000138:chemical synthesis*
D006574:Heterocyclic Compounds, 2-Ring; D009942:Organometallic Compounds; D011166:Porphyrins; D000644:Quaternary Ammonium Compounds; D013452:Sulfonium Compounds; D012428:Ruthenium; C494063:platynecine