PROFESSOR ROGER W. ALDER
Phone: 0117 9287657 FAX: 0117 9298611
E-mail: Rog.Alder@bristol.ac.uk
Nature doesn’t have a monopoly on interesting molecules; designing novel molecules that may have unusual properties is intellectually challenging, potentially valuable and also fun! These general ideas drive research in my group, but more specifically, our current interests are in three areas:
Isolation of a stable imidazol-2-ylidene carbene1 sparked intense activity and my group have made substantial contributions, so that we are one of the major players world-wide in this area, with our own clear-cut agenda. We showed (i) that imidazol-2-ylidenes were strong bases,2 (ii) developed chiral analogues, e.g. 1,3 (iii) prepared the first stable acyclic diaminocarbene 2, permitting the measurement of rotational barriers which give information on p-bonding in these species,4 (iv) found that simple carbenes like 3 only dimerise slowly at ambient temperatures,5 (v) prepared the first stable aminooxy- and aminothio-carbenes, e.g. 4,6 demonstrating that other elements than nitrogen can provide adequate stabilisation, (vi) found7 that unhindered diaminocarbenes complex with Li, Na, and even K species, e.g. we have determined the crystal structure of 5, and (vii) used density functional methods to study diaminocarbene structures, C-N bond rotation barriers, and barriers to dimerisation.8
Work in this area arose out of earlier studies on intrabridgehead chemistry, particularly with diamines like 6.9 More recently, we extended this chemistry to study bridgehead phosphorus species like 7 and 8,10 which show various interesting types of P…P interaction. In the course of these studies, we found that remarkable in/out-inversions occur at bridgehead phosphorus atoms, thus reaction of 9 with NaBH4 in CH3CN/H2O leads to 10 in which both phosphorus atoms have inverted!11
In the course of this work found a flexible stereoselective route to medium-ring cis-diphosphines like 11 and 12.12 In current work, we have shown that that catalytically-active complexes containing these ligands are readily prepared and can be used in cross-coupling reactions, allylic alkylations, hydrogenation, hydroformylation, etc.
Quaternary centres provide extensive conformational control in acyclic molecules, and calculations show that combining this with rigid side groups like aromatic rings will lead to highly organised structures.13 We showed14 that 13 can be polymerised by a novel anionic ring-opening reaction to give 14, whose all-anti (i.e. [aaa]n - fully extended) structure with transverse aromatic rings is proved by 1H NMR shifts caused by aromatic ring currents. We have also developed synthetic routes to specific oligomers, e.g. the pentamer, 14, n = 4, and are interested in conforamtionally-related, but electronically different polymers derived from monomers like 15. We have prepared the corresponding epoxide polymers from 16 which probably adopt helical [aag]n structures. Ultimately, we aim to develop materials that exhibit different chemistry in the x-, y-, and z-directions, as illustrated in 17.
1. Arduengo, A, J, III; Harlow, R. L.; Kline, M. J. Am. Chem. Soc., 1991, 113, 361.
2. Alder, R. W.; Allen, P. R.; Williams, S. J. J. Chem. Soc., Chem. Commun., 1995, 1267.
3. Williams, S. J., Ph.D. thesis, Bristol 1998.
4. Alder, R. W.; Allen, P. R.; Murray, M.; Orpen, A. G. Angew. Chem. Int. Ed. Engl., 1996, 35, 1121.
5. Alder, R. W.; Blake, M.E. Chem. Commun., 1997, 1513. [Full paper]
6. Alder, R W.; Butts, C P.; Orpen, A. G. J. Am. Chem. Soc., 1998, 120, 11526. [Full paper]
7.Alder, R. W.; Blake, M. E.; Bortolotti, C.; Bufali, S.; Butts, C. P.; Lineham, E.; Oliva, J. M.; Orpen, A. G.; Quayle, M. J. Chem. Commun., 1999, 241. [Full paper]
8. Alder, R. W.; Blake, M. E.; Oliva, J. M., J. Phys. Chem. A, 1999, 103, 11200. [Full paper]
9. For reviews see: Alder, R. W. Tetrahedron, 1990, 46, 683; Alder, R. W.; East, S. P. Chem. Rev., 1996, 96, 2097. [Full paper]
10. Alder, R. W.; Ellis, D. D.; Gleiter, R.; Harris, C. J.; Lange, H.; Orpen, A. G.; Read, D.; Taylor, P. N. J. Chem. Soc., Perkin Transactions 1, 1998, 1657. [Full paper]
11. R. W. Alder and D. Read, Angew. Chem. Int. Ed. Engl., 2000, accepted for publication.
12. Alder, R. W.; Ganter, C.; Gil, M.; Gleiter, R.; Harris, C. J.; Harris, S. E.; Lange, H.; Orpen, A. G.; Taylor, P. N. J. Chem. Soc., Perkin Transactions 1, 1998, 1643. [Full paper]
13. Alder, R. W.; Maunder, C. M.; Orpen, A. G. Tetrahedron Letters, 1990, 46, 6717; Alder, R. W.; Allen, P. R.; Anderson, K. R.; Butts, C. P.; Khosravi, E.; Martín, A.; Maunder, C. M.; Orpen, A. G.; St. Pourçain, C. B. J. Chem. Soc., Perkin Transactions 2, 1998, 2083. [Full paper]
14. Alder, R. W.; Anderson, K. R.; Benjes, P. A.; Butts, C. P.; Koutentis, P. A.; Orpen, A. G. Chem. Commun. 1998, 309. [Full paper]