Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended...

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Chemistry of π-extended Molecules Yuzuru Kanda Baran lab Group Meeting 5/7/16 polymer Harold Kroto passed away 30 Apr. 2016 http://www.extremetech.com/extreme/210872-extremetech-explains-what- is-moores-law http://www.telegraph.co.uk/obituaries/2016/05/02/sir-harold-kroto--obituary/ https://www.cheaptubes.com/product-category/multi-walled-carbon- nanotubes/ Chem. Rev. 2006, 106 , 11, 4455. Nature 2003, 424, 915. Dalton Trans. 2010, 39, 4107. JACS, 2012, 134 , 9380. Science 2015, 347, 646. 1996 Harold Walter Kroto Richard Errett Smalley Robert Floyd Curl 2010 Andre Konstantin Geim Konstantin Sergeevich Novoselov – Ultimate goal of π-extended molecules is application for nano devices oligothiophene Moore's law – the number of transistors in a dense integrated circuit doubles approximately every two years. ??? N NH N HN N NH N N N HN N N will not cover... corrole N NH N N corrin (GM; Tian, 2016) Phthalocyanine N N B F F catenane (GM; Ishibara, 2010) BODIPY rotaxane supramolecules fullerene isomers multi wall nanotubes carbon nanohorn S S S S S S S S π molecules = Flat 1. efficient electronic interactions between individual segments 2. efficient energy transfer 3. uniform molecular structure (uniform property) 4. robust and stable structure 5. easy to process (solubility, toxicity, reactivity) 6. mass production How many π electrons? Planar? Planar? 4n+2 4n aromatic antiaromatic nonaromatic nonaromatic Hückel system reverse in Möbius system

Transcript of Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended...

Page 1: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

Chemistry of π-extended MoleculesYuzuru Kanda Baran lab Group Meeting5/7/16

polymer

Harold Krotopassed away30 Apr. 2016

http://www.extremetech.com/extreme/210872-extremetech-explains-what-is-moores-lawhttp://www.telegraph.co.uk/obituaries/2016/05/02/sir-harold-kroto--obituary/https://www.cheaptubes.com/product-category/multi-walled-carbon-nanotubes/Chem. Rev. 2006, 106 , 11, 4455. Nature 2003, 424, 915. Dalton Trans. 2010, 39, 4107. JACS, 2012, 134 , 9380. Science 2015, 347, 646.

1996Harold Walter KrotoRichard Errett SmalleyRobert Floyd Curl

2010Andre Konstantin GeimKonstantin Sergeevich Novoselov

– Ultimate goal of π-extended molecules is application for nano devices

oligothiophene

Moore's law– the number of transistors in a dense integrated circuit doubles approximately every two years.

???

NNH

N HN

N

NHN

N

N

HN

N

N

will not cover...

corrole

NNH

N N

corrin (GM; Tian, 2016) Phthalocyanine

N NB

F F

catenane(GM; Ishibara, 2010)

BODIPY

rotaxane

supramolecules

fullerene isomersmulti wall nanotubes

carbon nanohorn

S

S

S

S

S

SS

S

π molecules = Flat

1. efficient electronic interactions between individual segments2. efficient energy transfer3. uniform molecular structure (uniform property)4. robust and stable structure5. easy to process (solubility, toxicity, reactivity)6. mass production

How manyπ electrons?

Planar?

Planar?

4n+2

4n

aromatic

antiaromatic

nonaromatic

nonaromatic

Hückel system

reverse in Möbius system

Page 2: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

β-position

Yuzuru Kanda

Porphyrin Rothemund Synthesis

NH H

O

H N

NH N

HN

1. cat. HCOOH2. Chloranil

~ 10% yieldafter 2-3 column

JACS. 1935, 57, 2010.JACS. 1936, 58, 625.

R

O

Hcat. H+

~ 60%R

NH HN H

O

R'

1. cat. H+

2. Ox

~ 60% N

NH N

HN

R

R'

R

R' OPRD. 2003, 7, 799.

N

N N

N

Ar

Ar

Zn

9.2 ppm9.4

10.3N

N NN

Ar

Ar

ZnN

N N

N

Ar

Ar

ZnAgPF6, CHCl330ºC, 5 h

w/ cat. I2, 5 min47% S.M. + 27% dimer + 4% trimer

purified by GPC

N

N N

N

Ar

Ar

Zn HH

128106 nmstable

soluble to CHCl3, THF

N

N N

N

Ar

Ar

Zn HH

10240.85 µm

C65536H83970N4096Zn1024 (M = 1,061,658)non detectable by MALDI-TOF

Chem. Eur. J. 2005, 11 , 3389.

NH HN

Me

Et

Me

Me

Et

Me Br

Cu(OAc)2

9% N

N N

N

Et

Me Me

Et

Et

Me

Et

Me

Cu

J. Chem. Soc. 1961, 2418.

NH HN

Mes

N N

Mes1. NXS; DDQ

2. Ni(OAc)2 NiX X

X = ClNa2S•9H2O

N

NS

N

NS

Mes

Mes

Ni

X = BrNaN3, CuI

NN

Mes

XX

N

NN

N

NN

Mes

Mes

Nimeso-position

X = BrNiCl2, PPh3

Zn

DMF, 45 ºC30 min, 90%[gram scale]

NN N

N

Mes

Mes

Ni

Norcorroleantiaromatic

ACIE. 2012, 51, 8542.Inorg. Chem. 2002, 51, 12879.Chem. Eur. J. 2012, 18 , 16129.aromatic nonaromatic

PPh3

TMS

TMS

TMS

H

O

H

MeLi TMSTMS 1. Li; H2SiCl22. CHBr3 Si

TMS

TMS

TMS

TMSBr Br

SiTMS

TMS

TMS

TMS

– air- and moisture- sensitive crystal– the first isolable dialkylsilylene

JACS. 2004, 126 , 9993.ACIE. 2014, 53, 1506.

KC8 Ni(II)-norcorrole

toluene, rt, 30 min97%

NN N

N

Mes

Mes

Ni

SiR

R

N

N N

N

Ar

Ar

Zn Ar'Ar'

12

DDQSc(OTf)3

N

N N

N

Ar

Ar

Zn Ar'Ar'

12

electronic wireextreme red-shift;

~3500 cm-1

Science 2001, 293, 79.J. Phys. Chem. A, 2003, 107 , 8792photonic wire

oxidative dimerization; ACIE. 1997, 36, 135.

selected examples of hetero-porphyrins

tBuSi

tBu

Cl Cl Li, Na

THF82%

SitBu

tBu in situ SitBu

tBuJACS. 1999, 121 , 9722.

✔ norcorrole (antiarom)✘ porphyrin (arom)

taking advantage of antiaromaticity

Chemistry of π-extended Molecules Baran lab Group Meeting5/7/16

18π1.47 ppm1.57

16π

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Yuzuru Kanda

N

N

N

N

Mes

MesMes

Mes

NiNH2

DDQ, TFA N

N

N

N

Mes

MesMes

Mes

Ni NN

NN

NN

Mes

MesMes

Mes

Ni

N

N

N

N

Mes

MesMes

Mes

Ni NN

NN

NN

Mes

MesMes

Mes

Ni N

N

N

N

Mes

Mes Mes

Mes

NiNN

NN

NN

Mes

Mes Mes

MesNiN

N

twisted angle = 300º

N

N N

HN

Ph

Ph

Ph

PhNi(acac)2

57%COOEtH

N

N N

N

Ph

Ph

Ph

Ph

EtOOC

NiN

N N

N

Ph

Ph

Ph

Ph Ni

H

COOEt

N

N N

NPh

Ph

Ph Ni

H COOEt

homoporphyrin

N

NH N

HN

Et

Et HN Et

Et

Et

Et

Et

Et

COOEt

N

NH N

HN

Et

Et Et

Et

Et

Et

Et

Et

NCOOEt

Δ or M+

aza-homoporphyrinunstable

[2+2]hν

50%

Möbius (4n)mederately aromatic

Hückel (4n+2)non-aromatic

CN

CNNC

NCD.A. w/

Hückel product

pureMöbius product

Nature, 2003, 426, 819.

phasechange

NH

CHO

MeSO3H; DDQ

DCM, 0 ºC, 2 h

F

FF

F

F N

NH N

HN N

HNN

NHArAr

Ar

Ar

Ar Ar

Ar

Ar

P4/P6/P8/P10 = 9:19:38:15 (%)TL, 2003, 44, 2505.

1. POCl3, Et3N, DCM2. POCl3, Et3N, toluene

P6N

N

NNH

Ar

Ar

Ar

Ar

N

NP

O

Ar

ArP

O

Möbius anti-aromatic (30π)stable @rt

ACIE. 2010, 49, 4950.

AcOH

NH

Ar

ArN

HN

Ar

Ar HNAr

N

HN

OF

FF

F

Möbius aromatic (28π)stable w/o metal @rt

JACS. 2009, 131 , 7240.

highly twisted and fully conjugated system; JACS, 2015, 137 , 142

Chemistry of π-extended Molecules Baran lab Group Meeting5/7/16

breaking aromaticity; TL, 1974, 36, 3155. JACS, 1975, 97, 6175

Möbius aromaticity; TL, 1964, 29, 1923.

Möbius strip– A surface with only one side and only one boundary.

OsMeOOC PPh3

2BF4

Planar Möbius aromaticy;Nat.Commun. 2014, 5, 3265

12.0811.94 ppm

9.489.04

16π

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Baran lab Group Meeting5/7/16Yuzuru Kanda

0D carbon material: Fullerene– the largest particle posessing wave-particle dualitytotal synthesis(?) of C60; Science 2002, 295, 1500.

O

Cl

6 stepsto prepare Cl

trimerization

TiCl4

FVP

1100 ºC0.1-1%

Name reactions in fullerene– Bingel reaction

C60DBU

tolueneEtO

O

OEt

O

Br– Prato reaction

R

O

H MeHN

O

OH toluene

C60

O

EtO

O

OEt

C60C60

NMe

R

H2O

H2O

Molecular surgery; Science 2011, 333, 613.

C60N N

Ar Ar

1-ClNaph260 ºC, 40 h

O2, hν

1-ClNaph, CS2rt, 23-27 h

29%

ArAr ArAr

[4+4]

ArArretro [2+2+2] OO

ArAr

NMMO

THFrt, 3 h89%

OO

ArAr

O

O

H2O OO

ArAr

O OHHO

H2O

120 ºC36 h

9,000 atmquant

OO

ArAr

O OHHO

P(OiPr)3

toluene120 ºC

15 h, 50%

ArAr[4+2] thenretro [4+4]

Al2O3

360 ºC, 1 h29%

H2O@C60X ray was taken as

(Ni-porphyrin)2H2O@C60

Chem. Eur. J. 2003, 9, 1600.

recent example; 2H2O@C70Nat. Chem. 2016, 8, 435.

kg-scale synthesis of corannulene; OPRD, 2012, 16 , 664.

MeCl Mg;

O

OMe

OMe

85%

Me H2SO4AcOH

71%

MeMe

MeO OMe

MeOH

MeMe

O O(COCl)2AlBr3

73% (2:1)

MeMe

O O

Girard reagent T

AcOH85%

MeMe

O N

3-pentanoneKOH

MeMeOH

MeMe

O

norbornadiene

Ac2O60% (2 steps)

MeMe

MeMe

NBSAIBN

90-95%

Br Br BrBr

Br

Br

Br

Br HCOOHEt3N, Pd/C

88%

NaOH aq.

79%

R

R

R

R

Corannulene

R = BrR = H

NH O

Me3N

Chemistry of π-extended Molecules

no column8 steps (8.7%)

1.3 kg preparedTCI: $814 /100 mg

Page 5: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

Me

O

Yuzuru Kanda

bent aromatics: [n.n']Paracyclophane

O

Br Br

O

Br Br

4-10

SS

O4-10

Na2SAl2O3

1. (MeO)2CHBF42. KOtBu

OO

4-10

SMe

SMe

1. (MeO)2CHBF42. KOtBu; DDQ O O

4-10

JOC. 2003, 68, 2089.

iPr MeSO

p-tolO

Li

TsSe

2

the smallest model for CNT

TsSe

GeranylClNaBH4

Me

Me

Me

Me

mCPBA;Et2NH

88%

Ox from less hinderd face

Me OH

(S)-Linalool

HN

O

NH

OH

TBAF, MS 3 Å;Ac2O, Et3N, DMAP

DMSO, 85ºC45%

single atropisomer

sanjoinine G1

F

NO2

Me

MeO

NBn2

OHMe

Me

OO2N

NHO

HN

OMe

MeBn2N

MeMe

OAc

NO2

F

Ph

NH2

OH

TBAF

THFMS 3 Å

40%

NO2

ONH

Ph

NO2

[2.2]Paracyclophane as a chiral auxiliary; JOC. 1991, 56, 5672.

JACS. 2002, 124 , 583.

n

n'

to close the ring...

RCMMcMurryRamberg-BäcklundWittig

NH

NH2

cyclophane closure in total synthesis

4 stepsN N

N

NMeOOC

N

N

H

COOMeinverse electron demand D.A.

N,N-diethylniline

100%

Rawal's intermediate8 steps (15.8%)3 steps N

HN

H

O

ACIE. 2002, 41, 3261.

Chemistry of π-extended Molecules Baran lab Group Meeting5/7/16

NCOCF3

F3COCNhν

33%octahedrane

[5-5-3-5-5-5-5-3-5-5]fused ring system

JACS. 2006, 128 , 16508.

shorter N-C bond

through-bond interaction

HO

HOOTs

ClOTBS

TESOTESO

Cl O

O

NHAc

H

HO

HOOTs

ClOTBS

HOO

Cl O

O

NHAc

H

CsF, MS

DMF, 100 ºC

Cs

HO

HO

ClOTBS

HOO Cl O

O

NHAc

H

60% + 8% regioisomerno atropisomer isolated

fijiolide A

JACS, 2015, 137 , 11278interesting reactivity of cyclophane

NNO

CF3O

F3C

NCOCF3F3COCN

not yet made!!! (calc. predicted inpossible)

Page 6: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

Chemistry of π-extended MoleculesYuzuru Kanda Baran lab Group Meeting5/7/16

1D carbon material: Carbon nanotube (SWNT)

Phanephos; JACS. 1997, 119 , 6207. (from Merk Process)

Phanephos

PPh2

PPh2

Br2, Fe

ratio?Br

Br Br

Br

triglyme, 230 ºC1/1 = S.M. + desired

+

1. tBuLi;MgBr2•Et2O;PPh2(O)Cl

2.

NaOH

PPh2

PPh2

O

OHOOC

OBzCOOH

OBz(R)

47% (2 steps)>99.5% ee

;

HSiCl3

p-xylene87%

R2R1

R3HNOMe

O

R2R1

R3HNOMe

O

[Rh(cod)Phanephos]OTf(1-2 mol%)

H2

MeOH, rtupto 99.6% ee

kinetic resolution of peroxides; JACS, 2007, 129 , 3836.Me OOH

Me

MeMe OOH

Me

Me

PAr2

PAr2

Ar = 3,5-Me2C6H3

L

86% ee

inseparable

HO MeMe

Me

1. Et3SiCl, Et3N2. TBAF

> 99%ee

L =

Me OOHMe

Me

sigma$90.10 /100 mg

chiral boronic acid containing cyclopropane; JACS, 2003, 125 , 7198.

OBH

OMeMe

MeMe

Me

MeOOC

Me

MeOOCB

OO

MeMe

MeMe

[Rh(cod)Cl]2 (3 mol%)Phanephos (6 mol%)

89%>99/1 cis/trans, 97% ee

R1

R2

R1

R2

enantioselective Cope rearrangement; Nat. Chem. 2012, 4, 405.(S)-L(AuCl)2 (5 mol%)

AgSbF6 (20 mol%)

98-23%93-58% ee

Me

OH

Me

NPth

eg)

Me LPtCl2AgBF4

Ph3COMe

Me

O

Me

O

MeEtR

61%87% ee

76%64% ee

O

MeR = F80%

81% ee

OH

LPtCl2, AgBF4 NCC6F5

TMDOMe, XeF2

R

FMe69%

10% eeF

OH

Me

enantioselective polyene cyclization; ACIE, 2008, 47, 6011. JACS, 2013, 135 , 628.

roll up

Page 7: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

Hex

Yuzuru Kanda

I

I

MeO OMe

Bpin Bpin

MeO

MeO

OMe

OMe

MeO OMe

I I

nBuLi(iPrO)Bpin

Ar-IPd(PPh3)4

Cs2CO3

toluene/MeOHm

m = 2, 2%m = 3, 10%m = 5, 10%

LiNaph

includes at leastone homo coupling

separableby column

MeO MeO

e–

m

m = 4, 43%m = 7, 52%m = 13, 36%

1-2. Itami's strategy; ACIE. 2011, 50, 3244.

MOMO

MOMO

I

I

Ni(cod)2bpy

27%

MOMO

MOMO

MOMO

MOMO

NaHSO4, airm-xyleneDMSO65%

[12]CPP

3 steps13% yield

OMOM

OMOM

OMOM

OMOM

1-3. Yamago's strategy; ACIE. 2010, 49, 757.

SnMe3

SnMe3

PtL2L2Pt

L2Pt PtL2

PtCl2(cod)

57%

L = codL = dppf

dppf91%

90º

Br2

49%[8]CPP

3 steps25% yield

approach towars the synthesis of uniform CNTs– 1.armchair CNT1-1. Bertozzi's strategy; JACS. 2008, 130 , 17646.

2. chiral CNT; Nat. Commun. 2011, 2:492.Hex

Hex

XX

X = BrX = Bpin

Miyauraborylation

91%

PtCl2(cod)CsF

74%

Hex

HexHex

Hex

Pt(cod)

Pt(cod)

Hex

Hex

(cod)Pt

(cod)Pt

Hex

Hex

PPh3

94%(6 isomers)

Hex

Hex

Hex

Hex

Hex

3.zigzag CNT: ???

CPP

CC

smaller ring size=> narrower HOMO-LUMO gap[5]CPP has smaller gap than OPP

small ring-size CPPs exhibitsstrong polyene like character

CPPsOPPs

JACS. 2011, 133 , 8354.

H2N

AcHN NHAc

NH2

1. NaNO2 HCl2. H2SO4

HN

NNN

N

HN

NN

NNN

NH2N

NH2

H2NOSO3H

24%+ 48% mono NH2+ di NH2 isomers

furanePb(OAc)4

THF, reflux79%

anti/syn = 77:23

OO

JOC, 1986, 51, 979

TCI[5]CPP.....¥39,000/ 20 mg[12]CPP...$1209.00/ 10 mg

Chem. Sci., 2015, 6, 2746.

high templow temp

Chemistry of π-extended Molecules Baran lab Group Meeting5/7/16

cycloacene(not yet made!!!)

Page 8: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

Yuzuru Kanda

OO

O

COOMeCOOMe

CuCl2, Pd/C

CO, MeOH92%

O

COOMeCOOMe

MeOOCMeOOC

1. LAH2. SOCl2, py3. KOtBu

O

Helv. Chem. Acta. 1980, 63, 1149.ACIE, 1987, 26, 892.TL, 1996, 37, 1983.TL, 1996, 37, 1987.

2 X D.A.

OO

OO

O O

1. TiCl4, LAH2. Ac2O, HCl

cyclacenes

O O

OO

O

O O

O

Hex

Hex

Hex

Hex Hex

HexHex

Hex

PCC

O

O O

O

Hex

HexHex

Hex

O

O

Graphene, 2D molecules

O

Ph

PhPh

Ph

PhPh

Ph

Ph Ph2

Ph

PhPh

Ph

Co3(CO)8

dioxane5 d, 100 ºC

71%

AlCl3CuOTf

CS2???%detected by TOF-MStoo broad signal to prove

"superacene"C222H42

M = 2709

ACIE, 1997, 36, 1603

Ar Ar

OH

I

Br Ar Ar

OMe

PhPhCAN

MeOHrt

quant1. LiNaph; Ar2CO

2. BF3•Et2OAr Ar

Ph

ArAr

Phe–

LiAr Ar

Ar Ar

H

HHHH

H

inperfectconjugation

SiHR2

SiHR2

LiNaph; I2

SiHR2

SiHR2 Si

Si

R R

R R

JACS. 2003, 125 , 13662X

Y

R R

R R nother examplesX, Y = B, C, N, Si, S, P

Helicenes: the first helicene was synthesized by R. Weitzenbock in 1918

2

1. hν, I2 propylene oxide 90 ºC, 48 h, 7%

2. TBAF3. Tf2O, py4. Pd(OAc)2, Et3N HCOOH10% (3 steps)

TIPSO

[16]heliceneknow to form< 1% isomer

ACIE. 2015, 54, 6847.

N O

COOHMe

NO2

NO2NO2

O2N

δ- δ+NO

COOHMe NO2

NO2

NO2O2N

racemic

(+)-[6]helixene

CT-complex

Chiral resolution; JACS. 1955, 77, 3420. JACS. 1956, 78, 4765.

repeat unitn: upto 6

COPVn; JACS. 2012, 134 , 19254.

RR

RR

R

RCT complex

formation

✔ R = Me✘ R = Et

Chemistry of π-extended Molecules Baran lab Group Meeting5/7/16

Page 9: Yuzuru Kanda Chemistry of -extended Molecules Baran lab ... · Chemistry of π-extended MoleculesBaran lab Group Meeting ... NaBH 4 Me Me Me Me mCPBA; Et 2NH 88% Ox from less hinderd

Yuzuru Kanda

OTBDMS

OTBDMS O

OS

O

p-Tol

DCM

–40 to –20 ºC51%

e.e. > 98%dearomatizedto increase reactivity

TBDMSO

OTBDMS

O

O

TBDMSO

OTBDMS

O

O

O

O

O

O

(P)

(M)

H

CAN60%

92% ee

DDQ88%

96% ee

O

MeO

HO

MeO

Me

Me

Me

O

OMe

Me

KHMDS18-crown-6

(1R, 4S) > 98% ee(1S, 4R) > 83% ee

MeOAc

Me(P) > 98% ee(M) > 83% ee

enantiodivergent approach; Chem. Comm. 2002, 1412.

oxy-Cope approach; TL, 2003, 44, 2167.

N MeMe

IN MeI

OH

Ph

Me 1. tBuOH2. MeI

PhMe

O

nBuLi

87%

(P)-[5]helicenesynthetic applicationJACS. 2010, 132 , 4536.

NH

NH

NHN

H

TFPB

1. (2 mol%)

2. benzoquinone

NO2R'

NMe

NH

Me

NO2

NMe

MeO

R69%

90% ee

NHEt

Et

Ph NO2

Ph

NO270%20% ee

55%70% ee

3D carbon material: diamond, carbon nanohorn, junction of CNTs etc...

Stella BPM 3709380,000 times heavier

than the earth

nanodiamond

nano-particlefluorescentlow toxicityhigh stability

NDNDair

425 ºC5 h

1. SOCl22. NH2R

ND support synthesis; JACS. 2009, 131 , 4594. JACS. 2006, 128 , 11635.

NDNHR

OO

OH

ND NH

ON3

ND NH

ON

N N

R

R = alkyl, FcHN

O

MeCN

))), 30 min

Cl2,hνND ClNH3, Δ

ND NH2

Chem. Eur. J. 2008, 14 , 1382.

OSi

RO ORNH

GlyPheGlyPhe OSi

RO ORNH

O

S

NH

NH

O

H

H

PhO

Ph

Me

Me

Me

Me

TIPS

TIPS

Me

Me

Me

MePh

Ph

G

GG

G

GG

GG

GG

GGG

GG

G

G

G GG

GGG

GG

GG

G GG

G G

1. o-xylene, reflux2. TBAF

other examples

pushing the synthetic limit...; ACIE, 2005, 44, 6348.

repeatthe cycle

22 nmC10113H9028Si128M = 134162

Chemistry of π-extended Molecules Baran lab Group Meeting5/7/16

Stevens rearrangement approach; JACS. 1994, 116, 5084.