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Background Baran Group Meeting 02/15/06 Platonic Hydrocarbons Ryan Shenvi What are the 'platonic hydrocarbons'? Platonic Solids: • Regular solids, regular polyhedra: convex polyhedra whose faces are equivalent, convex regular polygons. • Discovered 'first' by the neolithic Scots, ca. 1300-1400 BC. • Described mathematically by Theaetetus (417 BC-369 BC), who proved the existance of 5 and only 5 regular solids; included in Euclid's E l e m e n t s, Book X. Polyhedron Tetrahedron Hexahedron Octahedron Dodecahedron Icosahedron Faces 4 6 8 12 20 Edges 6 12 12 30 30 Vertices 4 8 6 20 12 Symmetry Group T d O h O h I h I h • Included in Plato's T i m a e u s as part of his 'theory of everything,' which assigned the regular geometry of the solids to each of the elements: earth, water, air, fire, and ether (an element of order or logic added to the original elements described by Emedocles of Agrigentum, 495-435 BC). • In 1852, Schläfli proved the existance of exactly six regular polyhedra in four dim- ensions and three in all higher dimensions (some may be familiar with the hypercube, or tesseract, of A W r i n k l e i n T i m e fame). geometric duals geometric duals Platonic hydrocarbons are the corresponding carbogens, where each vertex is a carbon, each edge a bond, and each face a ring. • Not all platonic solids translate to platonic hydrocarbons; limited by carbon valence, bonding angles, and strain. Octahedrane and icosahedrane have not been prepared, nor has unsubstituted tetrahedrane. • However, numerous inorganic molecules adopt these geometries: C 2 B 10 H 12 carboranes [Zr 6 Cl 18 ] 3– • Tetrahedrane and cubane have been called "super s-aromatic and super s-antiaromatic, respectively: Cyclopropane exhibits strong s-aromaticity as evidenced by its 1. large diamgnetic sus- ceptibility and anisotropy, 2. upfield shifts of attached protons, 3. shielding of protons above its ring and 4. a stabilization of 11.3 kcal/mol (compare 33.2 kcal/mol for benzene). Cyclobutane exhibits strong s-antiaromaticity: 1. similarity to cyclopropane's strain (27.5 vs. 26.5 kcal/mol), 2. abnormally low diamagnetic susceptibility, 3. deshielded 1 H and 13 C shifts. The knowledge at which geometry aims is knowledge of the eternal, and not of aught perishing and transient . . . My noble friend, geometry will draw the soul towards truth, and create the spirit of philosophy, and raise up that which is now unhappily allowed to fall down. . . Nothing should be more sternly laid down than that the inhabitants of your fair city by all means learn geometry. en arch hn o logoz kai o logoz hn proz ton qeon kai qeon hn o logoz In the beginning was the word (logos) and the word was with God and the word was God. –Plato (ca. 427-347 BC) “The Republic,” ca. 370 BC –St. John, (ca. 10 AD-100 AD) “The Gospel of John,” ca. 96 AD Planar cyclopropane, cyclobutane, tetrahedrane, and cubane dissected nucleus-independent chemical shift grids. Red and green points denote positive and negative NICS values, respectively
Transcript of Baran Group Meeting Background 02/15/06 · PDF fileBaran Group Meeting Background 02/15/06...
BackgroundBaran Group Meeting02/15/06
Platonic HydrocarbonsRyan Shenvi
What are the 'platonic hydrocarbons'?Platonic Solids:• Regular solids, regular polyhedra: convex polyhedra whose faces are equivalent, convex regular polygons.• Discovered 'first' by the neolithic Scots, ca. 1300-1400 BC.
• Described mathematically by Theaetetus (417 BC-369 BC), who proved the existance of 5 and only 5 regular solids; included in Euclid's Elements, Book X.
PolyhedronTetrahedronHexahedronOctahedronDodecahedronIcosahedron
Faces4681220
Edges612123030
Vertices4862012
Symmetry GroupTdOhOhIhIh
• Included in Plato's Timaeus as part of his 'theory of everything,' which assigned the regular geometry of the solids to each of the elements: earth, water, air, fire, and ether (an element of order or logic added to the original elements described by Emedocles of Agrigentum, 495-435 BC).• In 1852, Schläfli proved the existance of exactly six regular polyhedra in four dim- ensions and three in all higher dimensions (some may be familiar with the hypercube, or tesseract, of A Wrinkle in Time fame).
geometric duals
geometric duals
Platonic hydrocarbons are the corresponding carbogens, where each vertex is a carbon, each edge a bond, and each face a ring.
• Not all platonic solids translate to platonic hydrocarbons; limited by carbon valence, bonding angles, and strain. Octahedrane and icosahedrane have not been prepared, nor has unsubstituted tetrahedrane.
• However, numerous inorganic molecules adopt these geometries:
C2B10H12carboranes [Zr6Cl18]3–
• Tetrahedrane and cubane have been called "super s-aromatic and super s-antiaromatic, respectively: Cyclopropane exhibits strong s-aromaticity as evidenced by its 1. large diamgnetic sus- ceptibility and anisotropy, 2. upfield shifts of attached protons, 3. shielding of protons above its ring and 4. a stabilization of 11.3 kcal/mol (compare 33.2 kcal/mol for benzene). Cyclobutane exhibits strong s-antiaromaticity: 1. similarity to cyclopropane's strain (27.5 vs. 26.5 kcal/mol), 2. abnormally low diamagnetic susceptibility, 3. deshielded 1H and 13C shifts.
The knowledge at which geometry aims is knowledge of the eternal, and not of aught perishing and transient . . . My noble friend, geometry willdraw the soul towards truth, and create the spirit of philosophy, andraise up that which is now unhappily allowed to fall down. . . Nothingshould be more sternly laid down than that the inhabitants of your faircity by all means learn geometry.
en arch hn o logoz kai o logoz hn proz ton qeon kai qeon hn ologoz In the beginning was the word (logos) and the word was with God and the word was God.
–Plato (ca. 427-347 BC)“The Republic,” ca. 370 BC
–St. John, (ca. 10 AD-100 AD)“The Gospel of John,” ca. 96 AD
Planar cyclopropane, cyclobutane, tetrahedrane, and cubane dissected nucleus-independentchemical shift grids. Red and green points denote positive and negative NICS values, respectively
CO2Me
DodecahedraneBaran Group Meeting02/15/06
Platonic HydrocarbonsRyan Shenvi
(C10H10) + (C10H10) (C15) + (C5) (C16) + (C4)
Woodward et al,JACS, 1964, 3162.
FAILED
Eaton et al,JACS, 1972, 1014.
FAILED
heat, high pressure,irradiation, transitionmetals . . .
Paquette et al,JACS, 1978, 1600.
FAILED
Ni
CO2Me
CO2Me
H
MeO2C
CO2MeH
H
CO2Me
CO2Me
CO2Me
CO2Me
HHH
HH
CO2MeH
HH
H CO2Me
CO2Me
Na
H
MeO2C
CO2MeH
950 °C
I2, THF
–80 °C
+
++
1 : 1
OO
I
OO
I
CO2Me
CO2Me
O
O
KOH (aq.), MeOH;
(94%)
a) NaOH, MeOHb) H2SO4, Na2Cr2O7
c) Zn/Cu, MeOH(78%)
SPh Ph
(77%)
CO2Me
CO2Me
O
O
CO2Me
CO2Me
O
OMeO2C
CO2Me
O
O
O
OO
O
MeO2C
CO2Me
Cl
Cl
O
CO2MeOPh
CO2MeOPh
CHOOPhOHOH
CHOO
a) H2O2, MeOH
b) P4O10, MsOH(83%)
H2, Pd/C, EtOAc
(100%)
NaBH4, MeOH(81%)
HCl, MeOH
H
H(62%)
Li/ NH3, BOMCl
(48%)
a) hn b) TsOHc) HN=NH
(i-Bu)2AlH
b) Li/ NH3c) H3O+
PCC
b) hn c) TsOHd)HN=NH
Pd/ C
250 °C
a) hn
a) KOH, EtOH
I2, NaHCO3
(15-20%)
SUCCESS!Paquette, L. A.; Ternansky, R. J.; Balogh, D. W. JACS, 1982, 104, 4502
DODECAHEDRANE
first non-mesointermediate
Considerations:• tandem bond-forming events require proper alignment• severe entropic disadvantage in dimerization events• new bonds must form on the endo face
Late-stage reactions mustall be able to take place from the exo-face.
DodecahedraneBaran Group Meeting02/15/06
Platonic HydrocarbonsRyan Shenvi
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl S Cl
Cl
Cl
ClCl
Cl
Cl
Cl
Cl
Cl
Cl
ClCl
Cl
HH
Cl
Cl
Cl
ClCl
ClCl
Cl
ClCl(95%)
isodrin
H H
H2 transfer D
D
[–SO2]
Li, t-BuOH
S O OO O
ClCl
Cl ClA
a) A, Db) Li, t-BuOH
c) Pd/C, 250 °C(35%)
OO
O
O
O
O
O
N2
N2CO2MeMeO2C
Pt/Re/Al2O3/H2
250 °C(3 - 8%)
hn(30%)
OO O
PhH, D
Cu2O, bipy., H2O
a) B2H6•THF, quinoline, 150 °Cb) NaOH, H2O2c) CrO3, Me2CO
(73%)
a) HCO2Me, NaHb) TsN3, Et3N
(83%)
hn
MeOH(95%)
a) OH–
b) Pb(OAc)4, I2 CCl4, hnc) Na-K, THF; t-BuOH
(76%)
'black box'DHf
°
(Estr)64.4 (115.0)
22.2(68.9)
– 42.2 kcal/mol(–46.1)
Pagodane: 14 pots24% overeall (90%/step)
Prinzbach et al. Angew. Chem. Int. Ed. Engl. 1994, 2239. TETRAHEDRANE• Numerous attmpts towards its synthesis . . .
OH
H
N NO
O
OO O
NLiTs
TsLiNH
•O
" . . . leaving as the only consolation the knowledge of how not to make tetrahedrane." -Henning Hopf
• High-energy diradical-like intermediate can rapidly convert to its lower energy lumomer.
~126
~94
~22
~32
nearly equal energies of activation
E
Schematic representation of the MERP (minimum energy reaction path) for conversion of tetrahedrane to cyclobutadiene.
• High-energy diradical-like intermediate can rapidly convert to its lower energy lumomer.
'bonding' interactionbetween 'radicals,and s-conjugation
'anti-bonding' interactionbetween 'radicals and
through space interactionwith central bond
HOMO-LUMO crossingthrough diradical bicyclo-
butane
(kcal/mol)
t-Bu
t-Bu
t-Bu
t-Bu
decompositionproducts
H
H
H
H
Rxn Coordinate
E
any movement away tetrahdral geometry increases tert-butyl steric interactions, imparting kinetic stability
• Originally proposed and utilized by G. Maier et al in the first synthesis of a tetrahedrane
• However, tetrahedrane (Estr= 126-140 kcal/mol) can be stabilized by 'corset effect.'
Maier, G. et al Angew. Chem. Int. Ed. Engl., 1978, 520.
Platonic HydrocarbonsBaran Group Meeting02/15/06
Platonic HydrocarbonsRyan Shenvi
t-Bu
t-Bu
O
t-Bu
O
O
O
O
O
t-Bu
t-Bu t-Bu
H O
t-But-Bu
t-Bu H
O
Ht-Bu
t-Bu t-Bu
O
Brt-Bu
t-Bu t-Bu
O
t-But-Bu
t-Bu t-Bu
O
t-But-Bu
t-Bu t-Bu t-Bu
t-Bu
t-Bu t-Bu
t-Bu
t-But-Bu
t-Bu
•
t-Bu
Ot-Bu
t-Bu
t-Bu
+
t-Bu
t-Bu
hn hn
Br2, CCl4;6N KOH, 2d
(80%)
+
t-BuLi, DME–10 °C to rt
2d(22%)
hn (254 nm),8:3 t-hexane/
pentane(Rigisolve)–196 °C(35%)12%
13C NMR: d = 32.26, 28.33, 10.20mp = 135 °C
hn
130 °C,cyclosilane
hn (300 nm),rt
hn
TMS
TMS
CoTMS
TMS TMS
TMS TMS
TMS TMS
TMS
2–
2Li
CpCo(CO)2+
TMS
TMSTMS
TMS
Li, THF, rt
BrCH2CH2Br,THF (85%)
aromatic 6p e–
cyclobutadiene
TMS
TMS
TMS TMS
Li
TMS
TMS TMS
hn (254 nm),
pentane, –100 °C(50%)
R
TMS
TMS TMS
R = Me, H (2.85 ppm)
Me2SO4,C6D6, rt
ORC6D6,
rt
MeLi, THF, rt
(67%)
Sekiguchi, A. et al. JACS, 2003, 12684.
O
O Br
O 1. NBS2. Br2/ Br–
(40%)
O
Br
Br
O
CO2H
HO2C
O
O2t-Bu
O
t-BuO2
hn, MeOH, HCl
50% KOH (aq.) (30%)
1. SOCl22. t-BuO2H, Py.
diisopropylbenzene100 °C
Eaton, P. E. et al. JACS 1964, 962.Eaton, P. E. et al. JACS 1964, 3157.
R. Pettit and co-workers JACS 1966, 1328.
Fe(CO)3
O
OBr
Br
O
OBr
Br O
OBr
Brhn, PhH(90%)
+ CAN
3. Et3N
(prepared by Fluorochemin CA, and EniChem
Synthesis in Milan on a multi-kilogram scale)
DHf = 144-159 kcal/mol(calculated)
1H NMR: d = 4
Cubane (Hexahedrane)
CO2Me
MeO2C
Mg(TMP)2, THF
–78 °C; CO2(85%)
NCN(i-Pr)2
O
NCN(i-Pr)2
O
CO2H
a) CH2Cl2, (COCl)2; THF, NH3, –78 °Cb) CHCl3, DMF, TMEDA SOCl2, –10 °C
(99%)
(77%)
NCN(i-Pr)2
O
CN
BrMgTMP, THF,–78 °C;
CO2(90%)
NCN(i-Pr)2
O
CN
HO2Ca) CH2Cl2, (COCl)2; THF, NH3, –78 °C
b) SOCl2, D(90%)
NCN(i-Pr)2
O
CN
NC
HO2CN(i-Pr)2
O
CO2H
HO2CHO2C
a) BrMgTMP, THF, –78 °C; CO2b) KOH (aq), EtOH, D
(77%)
(100%)
AcOOAc
AcO OAcLAH, THF, D;
Ac2O,(89%)
DMDO, Me2CO;SOCl2; Barton'sNaNHPT, DMAP;
t-BuSH, hn, PhH (72%)
N(i-Pr)2
OAcAcO
AcOOAc
Eaton et al. JACS, 1993, 10202
NO2
CubaneBaran Group Meeting02/15/06
Platonic HydrocarbonsRyan Shenvi
OAcAcO
AcOOAc HO2C
CO2H
CO2HHO2C
O2NNO2
NO2O2N
10% NaOH (aq.)KMnO4
(85%)
SOCl2, MeCN;CH2Cl2, TMSN3;
CHCl3, D; DMDO, Me2CO, H2O
(30%)
O2NNO2
NO2O2NO2N
O2N
H
4 equiv. NHMDS,THF/MeTHF –78 °C;
N2O4, –130 °C,i-pentane;
H+, Et2O
(74%)
NO2O2NNO2
NO2O2NO2N
O2N
NO
NO2O2NNO2
NO2O2NO2N
O2N
NO2 LHMDS, CH2Cl2
–78 °C
O3
(45-55%)
DHf = 81-144 kcal/moldensity ~ 1,9-2.2 g/cm'leads to calculated detonation velocities and pressures much higher thanthat of TNT, 15-30% greater than HMXand perhaps even better than CL-20,the most powerful nonnuclear explosiveknown.'
NN
NN NO2
O2N
O2N
NO2
N
NN NNO2
N NO2N NO2
NO2
O2N NO2
O2N NO2
NO2
Me
TNT HMX CL-20
