Tanachat Worakun

The synthesis of fused ring nitrogen heterocycles via regiospecific intramolecular heck reactions

Abstract A series of palladium (and in some cases rhodium) catalysed regiospecific 5-exo-, 6-endo-and 6-exo-trig cyclisations of aryl iodides and vinyl bromides onto proximate alkenes or heteroaromatic rings (indole, pyrrole) lead to a wide variety of fused ring systems. In appropriate cases the methodology provides a facile approach to the creation of tetrasubstituted carbon centres. Double bond isomerisation in the product is only observed in a few cases.

Palladium catalysed tandem cyclisation-anion capture processes.Hydride ion capture by vinylpalladium species.

Abstract A new palladium catalysed-anion capture process is proposed, Examples are provided involving cyclisation of o-(ω-acetylenic)-aryl iodides and 2-bromo-1,6-enynes to heterocyclic- and carbocyclic-vinylpalladium species followed by hydride ion capture.

Regiospecific palladium catalysed tandem cyclisation-anion capture processes. Stereospecific group transfer from organozinc and organoboron reagents

Abstract Vinyl-, alkyl- and π-allyl-palladium species arising from regiospecific palladium catalysed 5- or 6-exo-dig or -trig cyclisations onto proximate alkynes, alkenes or dienes can be intercepted stereospecifically by organozinc or organo boron reagents leading to carbo-and hetero-cyclic compounds in moderate to good yield.

The regioselectivity of rhodium and palladium-catalysed cyclisations of 2-bromo-1,6- and -1,7-dienes

Abstract 2-Bromo-l,6-dienes are catalytically cyclised to a mixture of the corresponding 3,4-bis(methylene)cyclopentane and 5-methylenecyclohex-3-ene. Wilkinsons catalyst shows good selectivity for the 5-membered ring product whilst palladium catalysts, in general, show little selectivity, Addition of tetraethylammonium salts, especially the chloride, allow the palladium catalysed reactions to be carried out at 30°C in good yield and with high selectivity for the 5-membered ring. 2-Bromo-1,7-dienes are cyclised regio-specifically to 6-membered rings by the same catalysts although some double bond isomerisation also occurs. The mechanism of the catalytic cyclisations is discussed. The 3,4-bis(methylene) cyclopentanes undergo facile Diels-Alder reactions.

Regiospecific palladium catalysed tandem cyclisation-anion capture processes. Stereospecific group transfer from organotin reagents.

Abstract Vinyl-, alkyl- and π-allyl-palladium species arising from regiospecific palladium catalysed 5- or 6-exo-trig cyclisations onto proximate alkynes, alkenes or dienes can be intercepted by organotin reagents with stereospecific transfer of an organic group from tin leading to carbo- and hetero-cyclic compounds in moderate to good yield.

Palladium catalysed tandem cyclisation-anion capture processes.Hydride ion capture by alkyl- and π-allyl-palladium species

Abstract Alkyl- and π-allyl-palladium species arising from 5-exo-trig cyclisations onto proximate alkenes or dienes can be intercepted by hydride ion sources leading to carbo- and hetero-cyclic compounds usually in good yield.

Palladium catalysed tandem cyclisation - anion capture processes. Part 2. Cyclisation onto alkynes or allenes with hydride capture☆

Abstract A wide range of palladium catalysed regio- and stereo-specific 5-, 6- and 7-exo-dig mono-, bis- and tris-cyclisation processes of aryl and vinyl halides and allylic acetates are described. The mono- and bis-cyclisation processes terminate in hydride capture from piperidineformic acid or sodium formate. Addition of Tl 2 CO 3 results in alkyne-allene isomerisation and leads, after cyclisation, to 1,3-dienes which give Diels-Alder adducts in good yield.

The synthesis of bridged-ring carbo- and hetero-cycles via palladium catalysed regiospecific cyclisation reactions ☆

Abstract A catalyst system comprising 10 mol % (Pd(OAc) and 20 mol % PPh3 effects the cyclisation of aryl halides onto proximate alkenes via 5-, 6-, and 7-exo-trig, and 7-endo-trig processes giving a variety of bridged-ring carbo- and hetero-cycles in excellent yield. Double bond isomerisation in the product is rarley encountered and may be suppressed by the addition of Tl(1) salts. One example of diastereospecific bis-cyclisation is given and the crystal structure of 1-aza-2-sulphonyl-3,4-benzobicyc is reported.

Regiospecific palladium catalysed tandem cyclisation-anion capture processes. Carbon-, nitrogen- and oxygen-centred nucleophiles

Abstract π-Allyl- and alkyl-palladium species arising from regiospecific palladium catalysed 5-exo-trig cyclisations onto a proximate diene or alkene can be intercepted regiospecifically by stabilised carbanions, secondary amines or acetate ion giving carbo- and hetero-cyclic compounds good to excellent yields.

Regiospecific formation of 1,3-dienes by the palladium catalysed intra- and inter-molecular coupling of vinyl halides.1

Abstract Palladium acetate (5 mol %) effects catalytic inter-and intra-molecular coupling of vinyl bromides in good yield under mild conditions provided sufficient triarylphosphine and potassium carbonate are present to regenerate the active palladium(O) species. Wilkinsons catalyst is a poor catalyst for the same coupling reaction. Double bond isomerisation is not observed under these conditions. The palladium catalyst also couples iodobenzene to biphenyl in 48% yield whilst Wilkinsons catalyst is ineffective. The mechanism of the coupling process is discussed.