Norris Thompson

Synthesis and reactivity of hexahydropyrroloquinolines

Abstract Formal [4+2] cycloaddition of cyclic enamides with imines derived from aromatic amines gave the 4-arylhexahydropyrroloquinoline skeleton in one step as mixtures of diastereoisomers. Aromatic imines derived from formaldehyde and methylglyoxalate also participated in this chemistry, with the latter favouring formation of the endo -cycloadduct. The cycloadducts derived from methylglyoxalate were unstable and fragmented to give highly substituted quinolines under both neutral and basic conditions. Imines derived from 3-cyanoacrolein also underwent cycloaddition and gave an advanced potential precursor to martinellic acid, albeit with poor diastereoselectivity.

Synthesis of the heterocyclic core of the alkaloids martinelline and martinellic acid

Abstract The tricyclic core of martinelline and martinellic acid was rapidly assembled utilising an imino Diels–Alder reaction of an imine derived from cinnamaldehyde with a cyclic enamide. The cycloaddition was completely regioselective though the exo – endo selectivity was poor. These diastereoisomers were readily separated by flash chromatography and the relative stereochemistry of the exo -isomer confirmed by single crystal X-ray crystallography. This intermediate was converted to the central core of the aforementioned alkaloids in five additional synthetic operations.

Expedient synthesis of (+)-trans-5-allylhexahydroindolizidin-3-one

Abstract Treatment of the bicyclic iminium ion derived from 5-methoxyhexahydroindolizidin-3-one with allyltrimethylsilane gave exclusively the diastereoisomer in which the allyl group was axial. This substrate is a useful precursor to 5-propyl-3-alkylindolizidine alkaloids.

4-Phenyloxazolidin-2-ones and isoindolin-1-ones: chiral auxiliaries for Diels–Alder reactions of N-substituted 1,3-dienes

Terminally N-substituted dienes derived from 3-methylisoindolin-1-one, 4-isopropyl- and 4-phenyloxazolidin-2-one undergo Diels–Alder reaction with a range of activated dienophiles. The reactions reported are completely regio- and endo-selective, with the diastereoisomeric excess with respect to the auxiliary good to excellent in most of the cases reported. A model has been developed for rationalising the stereochemical outcome of these reactions.

Base catalysed decomposition of oxaziridines to yield N-unsubstituted aldimines

Abstract A range of oxaziridines bearing an α-hydrogen atom on the N-alkyl substituent react with tertiary amines at ambient temperature to yield N-unsubstituted aldimines.

Synthesis of (+)-piclavines A1 and A2

Abstract Piclavines A1 and A2 have been synthesised for the first time. The route is short with the key step being the reaction of a bicyclic N -acyl iminium ion with 3-trimethysilyl-1-decene. This convergent strategy gave exclusively compounds in which the pendant decenyl group was axial , as a 6:1 mixture of E : Z- alkene diastereoisomers. Reduction of the lactam carbonyl group gave a 6:1 mixture of piclavines A1 and A2.

Cycloheptatrienyl-phosphorus derivatives: an abnormal phosphonium salt hydrolysis

Abstract A variety of cycloheptatrienyl-phosphorus derivatives have been prepared. In no case was evidence obtained of contribution from norcaradiene forms. Attempts to prepare the corresponding ylide from cycloheptatrienyltriphenylphosphonium salts led to substitution of phosphine, as did reactions with a variety of nucleophiles, including hydroxide ion where the observed reaction is in conflict with earlier reports.

Calix[n]arene phosphine oxides. A new series of cation receptors for extraction of europium, thorium, plutonium and americium in nuclear waste treatment

A novel class of calixarene derivatives with phosphine oxide residues [Calix-(OCH2CH2POPh2)n] attached to the lower rim showing high efficiency in extraction of EuIII, ThIV, PuIV, and AmIV from simulated nuclear waste is reported.

Single electron transfer rate measurements interpretation when a radicalion bond cleavage reaction occurs within the encounter pair

Abstract The rate constant ( k t ) for electron transfer between a donor radicalanion and an acceptor can be determined by electrochemical methods when the so-formed acceptor radicaanion undergoes irreversible fragmentation. When fast bond clevage (rate constant, k r ) occurs within the encounter pair for electron transfer the experimental relationship between log k t and E ° D does not give sufficient information to define the parameters for electron transfer and bond cleavage of the acceptor molecule. The value of E ° A becomes uncertain within a small range. knowledge of k r removes this uncertainty in E ° A .

Cyclization of 2′-bromodeoxybenzoins: a new synthesis of 2-phenylbenzofurans

Reaction of 2′-bromodeoxybenzoins with copper powder in refluxing dimethylacetamide gives the corresponding 2-phenylfuran in good yields.