A new building block technique based on cycloaddition chemistry for the regiospecific linking of alicyclic sub-units as a route to large, custom-functionalised structures

Warrener, Ronald N.; Schultz, Austin C.; Butler, Douglas N.; Wang, Shudong; Mahadevan, I. B.; Russell, Richard A.

doi:10.1039/a700010c

Cited by 56 publications

(34 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Structure optimisation (AM1 method) 12 for the diaza-bridged compound 23 and the 7-oxanorbornane system 24 (prepared using the ACE route) 2 indicates that the interplanar angle between the dimethoxynaphthalene chromophores to be 78 deg for 23 and 87 deg for 24. This difference in geometry can be used to fine tune angular relationships and illustrates the value in having alternative coupling procedures to produce related but different ring-systems as spacer units.…”

Section: Methodsmentioning

confidence: 99%

The Preparation of Rigid Alicyclic Molecules Bearing Effector Groups from Alkene BLOCKs using s-Tetrazines and 1,3,4-Triazines as Stereoselective Coupling Agents

Warrener¹,

Margetić²,

Russell³

1998

Synlett

Self Cite

View full text Add to dashboard Cite

Alicyclic alkenes are reacted with s-tetrazines or 1,3,4-triazines to give fused aza or diaza-1,3-dienes which are further reacted with alkenes, thermally or under high pressure conditions (8-14 kbar), to form aza-bridged or diaza-bridged Diels−Alder products of rigid structure, some bearing multifunctionality, eg ligand + chromophore.Developing ways to couple different alicyclic alkenes together as the basis for the production of rigid products lies at the heart of our newly announced building BLOCK approach to ribbon molecule synthesis. The initial work featured the coupling of alkenes with ester-activated cyclobutene epoxides (the ACE reaction). 2 More recently, the aziridine equivalent (the aza-ACE reaction) has been realised and the thermally generated 1,3-dipole used as the cycloaddition reagent to link with alkenes (Scheme 1, top). 3 We now report that s-tetrazines and 1,3,4-triazines can be used to provide a Diels−Alder coupling process as an alternative method for assembling norbornene BLOCKs into rigidly constructed products, this time containing an azabicyclo[2.2.2]octene or diazabicyclo[2.2.2]octene as the rigid linking subunit (Scheme 1, bottom). Scheme 1The present coupling method exploits the ability of inverse electrondemand heterocycles 4 to react with ring-strained alkenes to produce fused aza-1,3-dienes which can be stored (if stable) as BLOCKs and made to react further with the same or other ring-strained dienophiles to produce Diels−Alder coupled products. The success of the reaction with s-tetrazines depended on the suppression of the prototropic rearrangement of 4,5-dihydropyridazines 3 (Diels−Alder active) to their 1,4-isomers 5 (Diels−Alder inactive) (Scheme 2). 5 This was achieved simply by the addition of triethylamine to the reaction mixture. Where the dihydropyridazine BLOCK is produced from norbornenes, the second cycloaddition step is best conducted at room temperature under high pressure conditions. 7 We were not concerned about such rearrangements in our earlier work on fused 3,6-dipyridylpyridazines 6, since both isomers produce the same oxidised ligand. 8Reaction of norbornene 1 (as the prototype A-BLOCK) with 3,6-di(2'-pyridyl)-s-tetrazine 2b (triethylamine, CH 2 Cl 2 , 2h, RT) formed the 3,4-dihydropyridazine 3b (1,3-diene, B-BLOCK). Without isolation, 3b was treated with a variety of dienophiles 7-10 (second dienophilic A-BLOCK, 2-3 equivalents excess) under high pressure (8-14 kbar, 16h) 7 to form the A+B coupled products 11-14 (see Table 1). 9 The stereochemistry of these coupled products was assigned on the basis of two distinctive 1 H NMR probes: the nOe between the endo-protons (cf Ha, Hb in 11) of the central diazabicyclo[2.2.2]octene ring and the upfield shift of the inward-facing methylene bridge proton when it is proximate to the shielding effect of the diazo bridge.The most significant feature of these coupling reactions was the high diastereoselectivity with single products formed in all cases: formation of products with exo-stereochemistry occurred with simple di...

show abstract

Section: Methodsmentioning

confidence: 99%

The Preparation of Rigid Alicyclic Molecules Bearing Effector Groups from Alkene BLOCKs using s-Tetrazines and 1,3,4-Triazines as Stereoselective Coupling Agents

Warrener¹,

Margetić²,

Russell³

1998

Synlett

Self Cite

View full text Add to dashboard Cite

show abstract

“…The molecular structure of the title compound was determined as part of a synthetic program designed to generate fiinctionalised cavity structures [1][2][3]. The X-ray analysis shows an absence of crystallographically imposed symmetry.…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of tetramethyl (1α,2β,3α,5α,6β,7α,8β,9α,11α,12β)-4,10-dioxahexacyclo[ 5.5.1.02,6.03,5.08,12.09,11]tridecane- 3,5,9,11-tetracarboxylate, C19H20O10

Mahadevan¹,

Russell²,

Warrener³

et al. 2002

Zeitschrift Für Kristallographie - New Crystal Structures

View full text Add to dashboard Cite

“…11 Porphyrin A-BLOCK 4 was treated with 3,6-di(2'-pyridyl)-s-tetrazine 9 (0.5 equivalent) in the presence of triethylamine and the solution pressurised at 14 kbar for 20 hours. Product 11 was isolated in 52% yield after chromatographic separation (silica, CH 2 Cl 2 , 5% EtOAc) and was characterised by NMR and mass spectrometry, 13 m/z 1465 (M+2H) 2+ .…”

Section: Bis-porphyrinsmentioning

confidence: 99%

“…9,10 In turn, these rigid norbornene BLOCKs are used in the ACE coupling protocol 11 for the synthesis of linked porphyrins, and in the ACE or s-tetrazine route 12 for the preparation of rigid bis-porphyrins. In this way, a range of geometrical variants of rigidly linked porphyrins can be produced as well as U-type systems containing two porphyrin units.…”

mentioning

confidence: 99%

Preparation of New Porphyrin blocks and their Application to the Synthesis of Spacer and Cavity Ribbon Structures

Warrener

Johnston

Günter

1998

Synlett

Self Cite

View full text Add to dashboard Cite

Fused-norbornene BLOCKs, formed by the condensation of porphyrin vic-diamines with polyalicyclic α-diones, have been used to produce mono-porphyrin systems linked to other effector units or new U-type cavity bis-porphyrins using ACE or s-tetrazine coupling protocols.The synthesis of structures incorporating a pair of porphyrins as functional units has been reported from a number of laboratories and these vary from systems where the porphyrins have rotational degrees of freedom 2-6 to those with rigidly positioned porphyrin moieties. 7,8 Such products have been employed as model photosynthetic systems for energy and electron transfer, and in artificial enzyme studies. We have sought general routes to bis-porphyrins as host systems for guest inclusion and have targeted rigid systems since these are most suitable for guest specificity.We report herein, methods for making porphyrin building BLOCKs utilising the condensation of alicyclic α diones containing a terminal norbornene subunit with o-phenylene diamines and employing the Crossley phenylenediamine 3 as the porphyrin source. 9,10 In turn, these rigid norbornene BLOCKs are used in the ACE coupling protocol 11 for the synthesis of linked porphyrins, and in the ACE or s-tetrazine route 12 for the preparation of rigid bis-porphyrins. In this way, a range of geometrical variants of rigidly linked porphyrins can be produced as well as U-type systems containing two porphyrin units.The first advance was to show that porphyrins 4 and 5 could be formed from the reaction of the Crossley diamine 3 with α-diones 1 and 2 respectively (Scheme 1). These condensations were carried out in dry, de-oxygenated pyridine or dichloromethane at ambient temperature, and following chromatographic separation (silica, CH 2 Cl 2 :petroleum spirit=1:3), isolated as crystalline solids: 4 (93%) and 5 (60%). These adducts were characterised by 1 H NMR and mass spectrometry. 13 Porphyrin Rods and SpacersNorbornene 4 was shown to serve as an A-BLOCK in ACE coupling by reaction with the cyclobutene epoxide B-BLOCK 6 to form the coupled product 7, where the porphyrin ring is rigidly linked to the dimethoxy naphthalene chromophore (Scheme 2, Route I). This coupling was achieved under thermal conditions (CH 2 Cl 2 , sealed tube, 160 o C, 2 days) and the same method can be used for coupling with other functionalised B-BLOCKs in the production of rigid spacer systems.The alternative approach to 7 (Scheme 2, Route II) highlights a new strategy for producing α-dione BLOCKs with inbuilt effector groups. Here, the cyclobutene epoxide B-BLOCK 6 is reacted site-specifically at the norbornene π bond of the enedione A-BLOCK 1, to form the new, functionalised α-dione BLOCK 8. The second step in this route involves condensation of the Crossley porphyrin diamine 3 9,10 with 8 to produce 7, which was identical with that produced in Route I. The availability of two different condensation/ACE coupling sequences to spacer molecule 7 demonstrates the versatility of using BLOCK techniques in this type of building proto...

show abstract

A new building block technique based on cycloaddition chemistry for the regiospecific linking of alicyclic sub-units as a route to large, custom-functionalised structures

Cited by 56 publications

References 10 publications

The Preparation of Rigid Alicyclic Molecules Bearing Effector Groups from Alkene BLOCKs using s-Tetrazines and 1,3,4-Triazines as Stereoselective Coupling Agents

The Preparation of Rigid Alicyclic Molecules Bearing Effector Groups from Alkene BLOCKs using s-Tetrazines and 1,3,4-Triazines as Stereoselective Coupling Agents

Crystal structure of tetramethyl (1α,2β,3α,5α,6β,7α,8β,9α,11α,12β)-4,10-dioxahexacyclo[ 5.5.1.02,6.03,5.08,12.09,11]tridecane- 3,5,9,11-tetracarboxylate, C19H20O10

Preparation of New Porphyrin blocks and their Application to the Synthesis of Spacer and Cavity Ribbon Structures

Contact Info

Product

Resources

About