Sterically and polarity-controlled reactions of tBuLi with P=CH-NR heterocycles: Novel heterocyclic P- and P,O-ligands and preliminary tests in transition-metal catalysis

Article abstract of DOI:10.1002/chem.200702016

(1R)-1,3-Benzazaphospholes 1a-c, P=CH-NR heterocycles of the indole type, react with tBuLi in two ways, depending on the steric demand of the N-substituent and the polarity of the medium. The presence of small N-alkyl groups induces CH-deprotonation in th

Full text of DOI:10.1002/chem.200702016

DOI: 10.1002/chem.200702016
Sterically and Polarity-Controlled Reactions of tBuLi with P=CH-NR
Heterocycles: Novel Heterocyclic P- and P,O-Ligands and Preliminary Tests
in Transition-Metal Catalysis
[
a]
[a]
[b]
Bhaskar R. Aluri, Markus K. Kindermann, Peter G. Jones, and
[
a]
Joachim Heinicke*
2
3
Abstract: (1R)-1,3-Benzazaphospholes
a–c, P=CH-NR heterocycles of the
5b was also observed. N-Neopentyl
groups, with intermediate steric
demand, give rise to formation of mix-
tures in ethers but allow switching
either to selective CH lithiation in
THF/KOtBu or to addition in pentane.
Bulkier N-adamantyl groups always
cause preferred addition. Protonation,
silylation, and carboxylation were used
to convert the P=CLi-NR, (E)-tBuP-
cies into the corresponding s -P or s -P
compounds 4b and 6a,b, 7b,c, or 8b–
10b with additional N and/or O donor
sites. Slow diffusion-controlled air oxi-
dation of 10b led to the meso-diphos-
1
indole type, react with tBuLi in two
ways, depending on the steric demand
of the N-substituent and the polarity of
the medium. The presence of small N-
alkyl groups induces CH-deprotonation
in the 2-position to give hetaryllithium
reagents 2a and 2b, whereas bulky N-
substituents and nonpolar solvents
change the reactivity towards addition
at the P=C bond. The preferred regio-
selectivity is tert-butylation at phospho-
rus, occurring with excellent diastereo-
selectivity for trans-adducts 3b and 3c,
but the inverse tert-butylation at C2 to
1
phine 11b. Preferred h -P coordination
was shown for an [Rh(cod)Cl] complex
A
H
R
U
12b, and the potential of the new li-
gands 4b and 7b in catalysis was dem-
onstrated by examples of Pd-catalyzed
CÀN coupling and Ni-catalyzed ethyl-
CHLi-NR, and LiP-CH(tBu)-NR spe-
A
H
R
U
G
ene oligomerization (TON>6300).
Crystal structures of 6b, 11b, and 12b
are presented.
Keywords: homogeneous catalysis ·
nickel oligomerization
phosphorus · rhodium
·
·
[2]
Introduction
nated phosphenes, bisphosphenes, or phosphaaromatics.
The latter class have so far found less application than phos-
phanes, but there are promising studies of the use of two-co-
ordinated phosphorus compounds, and in particular of func-
tionally substituted derivatives as hybrid ligands, in coordi-
Trivalent phosphorus compounds have found extensive ap-
plication in coordination chemistry and catalysis and cover a
wide range of ligand types and properties, from highly
[1]
[2,3]
basic and bulky donor phosphanes to p-acidic two-coordi-
nation chemistry and catalysis.
Furthermore, stable P=C
compounds possess broad but so far largely unexplored po-
tential for the synthesis of novel phosphane ligands. A re-
cently highlighted example is the anionic polymerization of
[
a] B. R. Aluri, Dr. M. K. Kindermann, Prof. Dr. J. Heinicke
Institut für Biochemie—Anorganische Chemie
Ernst-Moritz-Arndt-Universität Greifswald
Felix-Hausdorff-Str. 4, 17487 Greifswald (Germany)
Fax : (+49)3834-864377
[4]
MesP=CPh and copolymerization with styrene to produce
2
novel multiphosphane materials. It is based on addition of
organolithium species at the phosphorus-carbon double
bond, which has also been reported for other types of P=C
E-mail: heinicke@uni-greifswald.de
[
b] Prof. Dr. P. G. Jones
[5]
Institut für Anorganische und Analytische Chemie
Technische Universität Braunschweig, Hagenring 30
compounds. In continuation of our research on carbo- and
heterocyclically anellated azaphospholes and azaphospho-
3
8106 Braunschweig (Germany)
[6,7]
lides,
we have observed competition between addition of
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author: NMR data for
tert-butyllithium at the double bond of the P=CH-NR group
and CH-lithiation with bulky N-alkylated 1,3-benzazaphos-
3
b–5b, formed by lithiation of 1b in THF, tables with detailed X-ray
[8]
13
ACHTREUNG
structural data for 6b, 11b, and 12b, C NMR spectra of the reported
compounds.
4328
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 4328 – 4335

FULL PAPER
2
3
their conversion by electrophiles into new s - and s -P
hybrid ligands, and preliminary tests of their use in catalysis.
Results and Discussion
Treatment of 1-methyl-1,3-benzazaphosphole (1a) with
tBuLi (pentane) at low temperature in THF or diethyl ether
led in good yield to the P=CLi-NMe species 2a (Scheme 1),
which crystallized from THF/hexane as a m-C bridged dimer
with two THF molecules per Li ion. It is stable at room tem-
perature for up to 2 d and was treated with various electro-
[6]
philes to yield functionally substituted derivatives. It was
expected that bulkier N-substituents would further increase
the stability of related lithiophosphenes and tolerate harsher
reaction conditions, thereby extending the scope of coupling
reactions. Treatment of the bulkier N-neopentyl benzaza-
Figure 1. Molecular structure of 6b in the crystal. Ellipsoids are at 50%
probability. Selected interatomic distances [Š] and angles [8]: P3ÀC2
1.7255(12), P3ÀC3A 1.7619(13), N1 ÀC2 1.3798(15), C2ÀC131.4798(17);
C2-P3-C3A 88.35(6), N1-C2-P3 115.55(9), C2-N1-C7A 111.22(10), C2-
N1-C8 125.48(10); P3-C2-C13-O1 À170.06(10), P3-C2-C13-O2 10.30(15);
hydrogen bond O2–H02···O1#1: D–H 0.88(2), H···A 1.76(2), D···A
[8]
phosphole 1b with tert-butyllithium (À60 to 08C) and sub-
sequently with carbon dioxide and chlorotrimethylsilane,
however, showed more complex behavior. In THF solution,
CH-lithiation competes with addition of tBuLi at the P=CH
substructure, leading to a mixture of 2b, 3b, and 5b, charac-
2
.6430(13), a(DHA) 174.9(18).
A
H
R
U
G
known hydrogen-bonded dimers in the crystal (Figure 1).
The lack of zwitterionic properties indicates a low basicity
at nitrogen, attributable to inclusion of the nitrogen lone
electron pair into the aromatic p system. The yield (30%)
3
1
1
13
terized by NMR data ( P, H, C) and trapping reactions.
On treatment with CO and workup by silyl ester formation
2
2
and methanolysis, 2b was converted into the s -P-heterocy-
[6]
clic amino acid 6b (Scheme 1), which behaves like a normal
was considerably lower than observed for 6a from 2a
carboxylic acid, is soluble in ether, and forms the well
under equivalent conditions, because of the competing addi-
tion of tBuLi in the case of 1b.
The primary addition product
3
b was converted into 4b and
into the carboxylation product
b, both of which were identi-
7
fied by NMR in the crude prod-
uct mixture, in good agreement
with the NMR data for isolated
species obtained by independ-
ent synthesis (see below). The
formation of the dihydrobenza-
zaphosphole 4b from 1b and
tBuLi takes place quite rapidly
in THF, more slowly (over-
night) in diethyl ether, and not
at all in pentane, which is con-
sistent with the high reactivity
of 3b and deprotonative attack
on 1b in ethers to give 2b, or
on ethers themselves. The de-
protonation of ethers by reac-
tive branched alkyllithium re-
agents is well known in the lit-
[9]
erature.
The hetaryllithium
species 2b, however, is less re-
active and does not attack
ethers during its lifetime.
To find out the reason for the
unexpected addition of tBuLi
to the P=C bond of the elec-
Scheme 1. Sterically and polarity-controlled reactions of tBuLi with N-alkylbenzazaphospholes and conversion
with electrophiles (CO /ClSiMe or ClSiMe ).
2 3 3
Chem. Eur. J. 2008, 14, 4328 – 4335
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4329

J. Heinicke et al.
tronically highly stabilized ring system, the lithiation of 1b
was performed under varying conditions. When 1b was
treated with one to five equivalents of tBuOK and one
equivalent of tBuLi in THF at À788C and excess Me SiCl
3
was added to the resulting solution, only 2-(trimethylsilyl)-
benzazaphosphole (8b) was obtained, along with a small
amount of recovered 1b. Silylated tert-butyl-dihydrobenza-
zaphosphole 9b could not be detected, even in the crude re-
action mixture. This shows that highly polar additives such
as KOtBu favor the deprotonation of 1 over addition. The
facilitation of deprotonation reactions by Schlosser bases is
[10]
well known, but the suppression of addition at the P=C
bond in this way is novel and surprising, as the high polarity
of the metal-carbon bond in a Schlosser reagent should also
accelerate addition at P=C.
Figure 2. Molecular structure of (2R,3S,2’S,3’R)-11b in the crystal. Ellip-
soids are at 50% probability. Selected interatomic distances [Š] and
angles [8]: P3ÀP3’ 2.2367(4), P3ÀC2 1.8886(11), P3’ÀC2’ 1.8838(11), P3À
C3A 1.8146(12), P3’ÀC3A’ 1.8160(12), C2ÀN1 1.4691(14), C2’ÀN1’
As a countercheck, the lithiation reaction was performed
in the nonpolar solvent n-pentane. Quenching by methanol-
ysis provided 4b and 10b in a 75:25 molar ratio (by
1
1
8
.4694(14), N1ÀC7A 1.3885(14), N1’ÀC7A’ 1.3880(14); N1-C2-P3
05.77(7), N1’-C2’-P3’ 106.29(7), C2-P3-C3A 89.10(5), C2’-P3’-C3A’
9.22(5), C2-P3-P3’ 97.13(4), C3A-P3-P3’ 99.72(4), P3-P3’-C2’ 99.96(4),
1
H NMR integration of CMe3 signals), carboxylation fol-
P3-P3’-C3A’ 95.85(4).
lowed by silylation and methanolysis led to precipitation of
the zwitterionic heterocyclic phosphanyl amino acid (E)-7b
in 68% yield and a small amount of 10b in the remaining
solution, and trimethylsilylation of the primary lithium com-
pounds gave a mixture of 9b and 10b. Neither 8b nor 4b
could be detected in any of these reactions, indicating sup-
pression of CH deprotonation of 1b by tBuLi or 3b. The
major products were the E diastereoisomers of 9b, accom-
panied by minor amounts of 2-tert-butyl-dihydrobenzaza-
phosphole (10b), which was formed as a result of the oppo-
site regioselectivity in the addition step and methanolysis of
Scheme 2. Structural characterization of (E)-9b as (S,S) and (R,R) enan-
tiomer mixture by diastereoisomeric rhodium complexes 12b.
the PÀSiMe group in the workup. In this case both pairs of
3
1
31
diastereoisomers were detected by H and P NMR spectra,
but the E isomers are also favored for steric reasons. The E/
Z assignment of 9b and 10b was based on the strong dihe-
3
1
1
dral angle dependence of two-bond P– H coupling con-
stants. If the proton at C2 is in a trans position relative to
the phosphorus lone electron pair (E diastereoisomers) then
2
JP, H is small (4.6 and 1.7 Hz for (E)-9b and (E)-10b), while
2
[11]
if it is in cis position (Z diastereoisomers) J is large.
P, H
The E configuration with oppositely directed axial 2- and 3-
substituents, in this case determined by X-ray diffraction, is
also manifested in the symmetrical diphosphane meso-11b,
formed as single crystals by slow diffusion-controlled air oxi-
dation of 10b in methanol (Figure 2).
Since the highly air-sensitive mixture of 9b and 10b, syn-
thesized on a small scale, could not be separated in a con-
venient way, and in order to characterize concomitantly the
coordination properties of the ambidentate dihydrobenzaza-
phospholes with P and N donor sites, the mixture was treat-
Figure 3. Molecular structure of (2RS,3RS)-12b (the (S,S) enantiomer is
shown). Ellipsoids are at 30% probability. Hydrogen atoms and THF
(
0.5THF/(2RS,3RS)-12b) have been omitted for clarity. Selected intera-
A
H
R
U
G
tomic distances [Š] and angles [8]: C2ÀP 1.859(2), PÀC3A 1.817(2), PÀ
C131.908(2), Si ÀC2 1.939(2), RhÀP 2.3354(5), RhÀCl 2.3832(6), RhÀC21
2.218(2), RhÀC22 2.204(2), RhÀC25 2.123(2), RhÀC26 2.116(2), C21ÀC22
1.377(4), C25ÀC26 1.393(4), P-C2-N 93.95(6), C3A-P3-C2 89.32(9), P-Rh-
C21 162.38(7), P-Rh-C22 161.03(7), P-Rh-C25 96.75(7), P-Rh-C26
ed with a semi-equivalent of [Rh
Scheme 2). After concentration and overlayering with n-
hexane, single crystals of the air-stable dihydrobenzaza-
phosphole-Rh(cod)Cl complex 12b binding the ligand 9b
A
H
R
U
G
(
9
3.95(6), P-Rh-Cl 88.47(2).
ACHTREUNG
were obtained. The crystal structure analysis (Figure 3)
1
showed a racemate with square-planar rhodium and h -P co-
ordination of the ligand, without contacts of rhodium to ni-
fragment are in the typical range for Rh
plexes. Also typically, the RhÀC bonds trans to the phos-
A
H
R
U
G
A
H
R
U
G
[12]
trogen. The bond lengths and angles for the Rh
A
H
R
U
G
4330
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 4328 – 4335

Novel Heterocyclic P- and P,O-Ligands
FULL PAPER
phane donor atom are longer than those trans to chloride
and the corresponding C=C distances are shorter and
longer, respectively. The relative configuration of the asym-
metric carbon and phosphorus atoms in the depicted ligand
is (2S,3S). The (2R,3R) enantiomer is generated by the in-
version symmetry of the space group. The PÀC2 bond is, as
in toluene (1008C, 48 h). This reaction, recently reported for
[19]
catalysis by dppp/
nopyridine in 53% yield (after purification) in the presence
of 7.5/5 mol% 4b and [Pd (dba) ]. Catalysts formed from
A
H
R
U
G
A
H
R
U
G
provided N-mesityl-2-ami-
2
3
AHCTREUNG
2
3
4b and Pd(OAc) (5/5 mol% or 1/2 mol%) gave unsatisfac-
A
H
R
U
G
2
tory levels of conversion (yields after isolation 29 and 13%).
Further catalytic tests were performed with the benzaza-
phosphole-2-carboxylic acids 6a and 6b and the dihydro de-
rivative (E)-7b because they have a P-CHR-COOH sub-
expected, much longer than P=C in 1H-1,3-benzazaphosp-
2
holes and longer than PÀC3A (sp carbon), but considerably
shorter than PÀC3to the tert-butyl group. Conversely, the
C2ÀSi bond is much longer than the SiÀC bonds to the
methyl groups. The smallest angle within the five-membered
ring is that of C3a-P-C2, followed by P-C2-N. This is in ac-
cordance with the lower tendency to hybridization for ele-
ments of higher periods.
_
À
structure, as did the early PO –nickel chelate catalysts for
[
20]
the Shell Higher Olefin Process.
weakly P-basic, rather p-acidic benzazaphospholes 6a or
6b and [Ni(cod) ] were inactive, those with (E)-7b were
highly active. Addition of ethylene to a solution of (E)-7b
and [Ni(cod) ] (each 65 mmol) in toluene at a starting pres-
sure of ca. 50 bar (12.3g C H ) and with heating at 708C led
While solutions of the
[6]
AHCTREUNG
2
To find out whether greater steric hindrance can lead to
addition even in polar solvents, and also to improved regio-
ACHTREUNG
2
2
4
[8]
selectivity, 1-adamantyl-1,3-benzazaphosphole (1c)
was
to efficient oligomerization with >94% conversion of ethyl-
ene (TON >6360). The reaction was complete within 1 h, as
shown by the pressure–time plot (Figure 4). The reaction at
treated with tBuLi in diethyl ether (À60 to 208C, 5 h) and
subsequently with CO . For easier workup the carboxylate
2
was silylated with Me SiCl and the ester was cleaved with
3
31
methanol. P NMR monitoring of the crude product re-
vealed formation of 7c but neither 6c nor a secondary phos-
phane 10c. Crystallization from CH Cl /hexane provided mi-
2
2
crocrystals of the heterocyclic a-phosphanyl amino acid (E)-
2
7
c. The E configuration is indicated by the small J cou-
P, H
pling constant (3.2 Hz). Diastereoisomers of Z configuration
could not be detected. As the five-membered ring is no
longer part of the aromatic system after addition of tBuLi at
the P=C bond, the nitrogen lone electron pair causes N-ba-
sicity and a zwitterionic structure in (E)-7b or (E)-7c, indi-
cated by a strong downfield shift (Dd=0.8 to 1.2) of the ad-
jacent CH-2 proton signal relative to those of its counter-
parts in 4b and 9b. Competing protonation at phosphorus
cannot be detected by NMR, although tert-butyl and o-ami-
noaryl (+M) substituents cause relatively high P-basicity.
The phosphorus resonance is observed in the usual phos-
phane region. However, an indirect hint at increased P-ba-
sicity is given by the high sensitivities of (E)-7b and (E)-7c
to hydrolysis by water, as observed for acyclic a-phosphanyl
Figure 4. Pressure–time plot for batch polymerization of ethylene in tolu-
ene in the presence of 7b/[Ni
A
H
R
U
G
2
] (solid line). The reaction is faster
(cod) (115/106 mmol) at
than with 2-diphenylphosphanylphenol/[Ni
A
H
R
U
G
2
]
[21]
7
08C (dotted line).
708C is faster than the oligomerization in the presence of 2-
diphenylphosphanylphenolate/[Ni(cod) ] catalysts, prefera-
AHCTREUNG
2
[21]
bly performed at 80–1008C, , and the average molecular
weight is considerably lower. Here, along with a small
amount of liquid oligomers, a waxy polymer (m.p. 115–
1178C, MNMR 725, a/internal olefins 78/22%, Me/Vin 1.6/1)
was obtained, consisting mainly of linear a-olefins, as is typi-
[13]
amino acids,
which gives evidence of the acetal-like
nature. In the absence of the COOH group or acid the dihy-
drobenzazaphospholes are stable to water, like acetals in the
presence of tertiary amines. In an early report on dihydro-
benzazaphospholes obtained by cyclocondensation of P-sec-
ondary 2-phosphanylanilines with aldehydes and ketones,
cal for SHOP-type catalysts. This suggests that, as shown for
_
[20]
À
phosphanylacetic acid nickel catalysts, a PO -chelate
structure is formed, stabilizing the catalyst.
[14]
sensitivity to hydrolysis was not mentioned.
The P-basicity and presence of bulky P-tBu substituents
in the above adducts suggested that they might be useful li-
gands in palladium-catalyzed coupling reactions. It is known
Conclusion
[15]
that aryl aminations (Buchwald–Hartwig aminations), im-
portant in view of the large number of bulk and fine chemi-
In conclusion, we have shown that electron-rich P=CH-NR
heterocycles, which, like diagonally related indoles, usually
undergo C2 lithiation by tBuLi in polar solvents, are driven
towards addition at the P=C bond by the presence of bulky
N-substituents. The reaction of N-neopentyl-1,3-benzaza-
phosphole, occupying an intermediate position and affording
a mixture in THF, can be controlled by the polarity of the
medium. Addition of KOtBu leads to a strong preference
[16]
cals containing aryl amines as substructures, are favored
[17]
by basic and bulky ligands. The starting materials for the
[8]
N-aryl-1,3-benzazaphospholes and related N-aryl-pyrido-
[18]
1
,3-azaphos
A
C
H
T
R
E
U
N
G
pholes
are also synthesized by this coupling.
This prompted us to test 4b in the coupling of 2-bromopyri-
dine with 2,4,6-trimethylaniline in the presence of NaOtBu
Chem. Eur. J. 2008, 14, 4328 – 4335
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4331

J. Heinicke et al.
for CH lithiation, suppressing addition, whereas nonpolar
hydrocarbon solvents have the opposite effect, furnishing
addition products only, with a preference for tert-butylation
at phosphorus and high diastereoselectivity for the trans
adduct in this case. The less favored addition of the tert-
butyl carbanion at C2 is completely suppressed in the case
of the bulkier N-1-adamantyl group. Substitution of the ben-
zazaphospholyl- or P-tert-butyldihydrobenzazaphospholyl-
lithium reagents by electrophiles allows access to novel
functionally substituted s - or s -phosphorus compounds.
This allows coordination chemical and catalytic studies with
novel P=C carboxylic acid derivatives or heterocyclic a-
phosphanyl amino acids.
(0.16 mL, 1.27 mmol) was added dropwise. After the system had warmed
to room temperature (2 h), THF was evaporated in vacuum, excess dry
MeOH (8 mL) was added, and after the system had been stirred for 2 h,
3
methanol and Me SiOMe were removed in vacuum. The residue was ex-
tracted with diethyl ether, and the ether layer was washed twice with de-
gassed aqueous H SO (10%). The ether layer was then washed with de-
2
4
Table 1. Crystallographic data.
6
b
11b
12b
2
3
empirical for-
mula
C
13
H
16NO
2
P
C
32
H
50
N
2
P
2
C
29
H
50ClNO0.5PRhSi
formula
weight
T [K]
249.24
133(2)
524.68
618.12
100(2)
133(2)
l [Š]
0.710730.71073 0.71073
monoclinic
P2 /n
crystal system monoclinic
monoclinic
space group
unit cell di-
mensions
a [Š]
b [Š]
c [Š]
P2
1
/c
1
1
P2 /n
Experimental Section
All reactions were performed under dry nitrogen or argon with use of
Schlenk techniques and freshly distilled, ketyl-dried solvents. NMR sol-
5.8021(4)
13.0437(8)
16.5657(10)
90
13.4813(3)
13.8134(3)
16.9844(3)
90
9.4178(6)
36.045(2)
9.4470(6)
90
109.623(4)
90
3020.7(3)
4
1.359
vents were dried (C
and recondensed in vacuum before use. Me
vacuum. The synthesis of 1b and 1c has been reported separately.
6
D
6
and [D
8
]THF over LiAlH
4
, CDCl
3
over P
4
O
10
)
3
SiCl was also recondensed in
a [8]
[
8]
b [8]
g [8]
V [Š ]
Z
93.6
90
1251.21(14)
4
1.323 Mg
0.209
101.177(2)
90
3102.89(11)
4
1.123
0.162
Other chemicals were used as purchased. NMR spectra were recorded on
multinuclear FT-NMR ARX 300 or Avance 300 (Bruker) spectrometers
3
1
13
31
at 300.1 ( H), 75.5 ( C), and 121.5 MHz ( P). Shift references are tetra-
1
13
31
À3
methylsilane for H and C NMR and H
3
PO
4
(85%) for P NMR. Cou-
1
calcd [Mgm
]
1
13
À1
pling constants refer to JH,H in H NMR and JP, C in C NMR data unless
stated otherwise. Assignments are supported by additional DEPT meas-
urements. Assignment numbers are given in Scheme 1; selected spectra
are found in the Supporting Information. Mass spectra were recorded on
an AMD40 (Intectra) single-focusing mass spectrometer. HRMS meas-
urements were carried out in Gçttingen with a double focusing sector-
field instrument MAT 95 (Finnigan) by EI (70 eV, PFK as reference sub-
m [mm
(000)
]
0.767
1304
F
A
H
R
U
G
528
1144
crystal size
[mm ]
q range for
data collec-
tion [8]
0.25”0.20”0.20 0.35”0.25”0.11 0.30”0.25”0.20
3
1.99 to 30.51
2.60 to 30.03
2.26 to 30.51
stances) or by ESI in MeOH, MeOH/NH
APEX IV Fourier transform ion cyclotron resonance mass spectrometer
Bruker Daltonics). Melting points were determined with a Sanyo Gal-
4
OAc, or MeCN with a 7 T
index ranges
À8ꢁhꢁ8,
À18ꢁkꢁ18,
À23ꢁlꢁ23
19962
À18ꢁhꢁ18,
À19ꢁkꢁ19,
À23ꢁlꢁ23
79976
À13ꢁhꢁ13,
À51ꢁkꢁ51,
À13ꢁlꢁ13
58573
(
lenkamp melting point apparatus in capillaries (uncorrected).
reflections
collected
independent
reflections
completeness 100.0
to q=30.008
Lithiation of 1b in THF: tBuLi (1.5m pentane solution, 0.23mL,
3818 [R-
9069 [R-
9122 [R-
0
.34 mmol) was added dropwise at À608C to 1b (64 mg, 0.31 mmol) in
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
THF (2 mL). This mixture was allowed to warm slowly to À408C and
99.8
99.6
stirred for 4 h. The solvent was removed in vacuum to give an orange-
3
1
yellow crystalline residue. The P NMR spectrum showed sharp signals
for 2b (d=104.3ppm) and 4b (d=À9.1 ppm) and two small but broad
signals in the phosphane and phosphide regions (d=5.3, À41.6 ppm), ten-
[
%]
absorption
correction
none
semiempirical
from equiva-
lents
semiempirical from
equivalents
1
tatively assigned to 3b and 5b; H integration of tBu signals (of neopen-
tyl group) ca. 40:28:17:15 (for equal intensity order). Compound 2b:
1
3
max. and min.
transmission
refinement
method
1.000 and 0.9830.8618 and 0.7192
H NMR ([D
8
]THF): d=0.93(s; CMe
3
), 6.73(tm, J=7–8 Hz, 1H; H-5),
3
4
3
6
7
(
1
6
(
.92 (td, J=7–8, J=1.6 Hz, 1H; H-6), 7.38 (d, J=8.2 Hz, 1H; H-7),
3
4
3
13
1
full-matrix
full-matrix least- full-matrix least-
.62 ppm (dt, J=7.6, Jꢀ JP,H ꢀ1.5 Hz, 1H; H-4); C{ H} (DEPT) NMR
2
2
3
least-squares on squares on F
squares on F
[D
8
]THF): d=29.66 (CMe
3
), 35.47 (CMe
3
3
), 65.10 (d, J=7.3Hz; NCH
2
),
2
3
F
12.75 (d, J=1.3Hz; CH-7), 116.15 (d, J=6.4 Hz; CH-5), 118.47 (CH-
), 126.39 (d, J=12.2 Hz; CH-4), 149.44 (d, J=8.9 Hz; C
2
2
data/re-
straints/pa-
rameters
3818/0/158
9069/0/337
9122/82/359
q
-7a), 150.03
1
1
d, J=60.5 Hz; C
q
-3a), 253.11 ppm (d, J=109.9 Hz; CLi-2). These NMR
data, except for those relating to the different N-substituent, are closely
similar to those of pure 2a, characterized unambiguously by X-ray crys-
tallography as the m-CLi-bridged dimer with two THF molecules per lith-
goodness-of-
1.0231.027
1.040
2
fit on F
[
6]
final R indices R1=0.0366,
R1=0.0359,
wR2=0.0949
R1=0.0389,
wR2=0.0838
ium. Data for 4b are in good accordance with those of independently
synthesized 4b recorded in C (see below).
-(2,2-Dimethylpropyl)-1H-1,3-benzazaphosphole-2-carboxylic acid (6b):
[
I>2s (I)]
wR2=0.0912
6
D
6
R indices (all
data)
R1
wR2
largest diff.
1
tBuLi (1.7m in pentane, 0.75 mL, 1.27 mmol) was added dropwise at
À608C to 1b (217 mg, 1.05 mmol) in THF (3mL). This mixture was al-
lowed to warm slowly to 08C over 5 h. The resulting orange-yellow solu-
0.0600
0.1021
0.451 and
0.0567
0.1000
0.809 and
À0.297
0.0560
0.0897
1.004 and À0.641
tion was cooled to À608C, and excess CO
solution for 1 h (color change to yellow). The mixture was stirred at
room temperature overnight and was then cooled to À608C, and Me SiCl
2
gas was passed through the
peak and hole À0.182
À3
[
eŠ
]
3
4332
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 4328 – 4335

Novel Heterocyclic P- and P,O-Ligands
FULL PAPER
gassed water, dried over Na
vacuum left a yellow viscous oil. Crystallization from CH
gave single crystals (crystal data see Table 1). By concentration of the
mother liquor a second fraction of white crystals, contaminated with
2
SO
4
, and filtered. Removal of solvent under
Cl /hexane
temperature and stirred for 5 h. The resulting orange-yellow solution was
cooled to À608C. Gaseous CO
period of 90 min, leading to a color change from orange to yellow. A
slight excess of Me SiCl (0.06 mL, 0.50 mmol) was added at the same
2
(from dry ice) was introduced over a
2
2
3
small amounts of 4b and 7b, was obtained (total 118 mg). Yield of pure
temperature, and the mixture was stirred at room temperature overnight
(colorless). Insoluble materials were filtered off and washed thoroughly
with ether. Removal of the solvent gave a colorless semicrystalline slush.
Treatment with dry MeOH (5 mL) and removal of volatiles in vacuum
1
6
b 79 mg (30%). Compound 6b: H NMR ([D
8
]THF): d=0.90 (s, 9H;
2
2
CMe
NCH
3
), 4.32 (brd, J=14.1 Hz, 1H; NCH
2
4
), 5.50 (brd, J=14.1 Hz, 1H;
3
4
2
), 7.13(tdd, J=7.9, 7.0,
J
P,H =1.6, J=0.6 Hz, 1H; H-5), 7.40 (tt,
3
4
5
3
J=8.7, 6.9, J+ JP, H =2.3Hz, 1H; H-6), 7.83(brd, J=8.7 Hz, 1H; H-7),
provided a solid that was recrystallized from CH
orless microcrystals of 7c (80 mg, 47%).M.p. 195–1968C; H NMR
2 2
Cl /hexane to give col-
3
3
1
8
.03(brdd, J=7.9, JP,H =4.3Hz, 1H; H-4), 10.60 ppm (vbrs, 1H; OH);
1
3
1
4
3
C{ H} (DEPT) NMR ([D
8
]THF): d=28.69 (s; CMe
3
), 35.96 (d, J=
(CD
2
Cl
2
): d=0.98 (d, JP, H =12.7 Hz, 9H; CMe
3
), 1.73(brs, 6H; d-CH
2
),
3
2
1
.8 Hz; C
q
Me
3
), 55.37 (d, J=3.8 Hz; NCH
2
), 116.08 (s; CH-7), 121.03(d,
2.06 (brd, J=11.9 Hz, 3H; b-CH2a), 2.14 (brs, 3H; g-CH), 2.32 (brd,
J=11.9 Hz, 3H; b-CH2b), 4.75 (d,
3
4
2
2
2
J=13.0 Hz; CH-5), 126.91 (d, J=3.4 Hz; CH-6), 130.07 (d, J=21.9 Hz;
J
P, H =3.2 Hz, 1H; PCHN), 6.65 (tdd,
1
2
3
4
4
3
CH-4), 142.46 (d, J=37.0 Hz; C
q
-3a), 147.29 (d, J=7.7 Hz; C
-2), 165.74 ppm (d, J=21.8 Hz; C
q
-7a),
J=7.2, JP, H =2.5, J=0.7 Hz, 1H; H-5), 7.05 (brd, J=8.4 Hz, 1H; H-7),
3
4
3
3
1
2
7
.17 (tdd, J=8.4, 7.2, J=1.5 Hz, 1H; H-6), 7.28 ppm (td, J= 7.2, JP, H =
1
62.65 (d, J=53.0 Hz; C
q
q
-COOH);
4
+
13
1
3
1
1
6.4, J=1.5 Hz, 1H; H-4), OH/NH below 12.5 ppm or vbr; C{ H}
P{ H} NMR ([D
8
]THF): d=118.71 ppm; MS (EI, 70 eV, 208C): m/z
2
+
+
(DEPT) NMR (CD Cl ): d=26.06 (d, J=15.3Hz; CH ), 30.54 (s; CH),
(
%): 250 (16) [M+1] , 249 (100) [M] , 193(80), 161 (46), 148 (5 )3 ;
2
2
3
1
+
3 2 2
31.75 (d, J=23.4 Hz; CMe ), 36.74 (s; CH ), 40.21 (s; CH ), 57.38 (brs;
NC -1’), 59.86 (brd, J=25.1 Hz; PCHN), 112.33 (s; CH-7), 116.52 (d,
q
HRMS (ESI): m/z: calcd for C13
H
16NO
2
P [M+H ]: 250.09916 (100);
1
found: 250.09914.
4
1
J=9.1 Hz; CH-6), 122.77 (d, J=9.1 Hz; C
q
-3a), 130.11
-7a), 177.82 ppm (d, J=16.5 Hz;
): d=7.37 ppm; HRMS: m/z: calcd for
P 371.2014; found: 371.2010.
-tert-Butyl-1-(2,2-dimethylpropyl)-2,3-dihydro-1H-1,3-benzazaphos
4b) and 2-tert-butyl-1-(2,2-dimethylpropyl)-2,3-dihydro-1H-1,3-benzaza-
A
H
R
U
G
1
-(2,2-Dimethylpropyl)-2-trimethylsilyl-1H-1,3-benzazaphosphole (8b):
2
2
(
d, J=24.3Hz; CH-4), 152.48 (s; C
q
KOtBu (800 mg, 6.53mmol) was added at À788C to a solution of 1b
3
1
CO);
C H30NO
22 2
2 2
P NMR (CD Cl
(
174 mg, 0.85 mmol) in THF (5 mL) to give a yellow solution. tBuLi
(
0.52 mL, 0.89 mmol) was then added dropwise at the same temperature.
3
(
A
C
H
T
R
E
U
N
G
phole
This mixture was stirred for 4 h, while slowly warming to À108C. The re-
action mixture was again cooled to À788C, and excess Me SiCl (1.07 mL,
.48 mmol) was added dropwise, followed by stirring overnight at room
temperature. THF was removed from the reaction mixture, and dry
MeOH was added to quench unconverted tBuLi and Me SiCl. After the
3
phosphole (10b): tBuLi (1.5m in pentane, 0.31 mL, 0.47 mmol) was
added dropwise at À308C to 1b (80 mg, 0.39 mmol) in pentane (2 mL).
This mixture was allowed to warm slowly to room temperature and
stirred for 20 h. Excess dry MeOH was added at room temperature to
the reaction mixture, which was stirred overnight. Insoluble materials
were filtered off and washed thoroughly with pentane. The solvent was
removed under vacuum to give a colorless solid (100 mg, 97%) consisting
8
3
system had been kept for 4 h at room temperature, excess MeOH was re-
moved under vacuum. The residue was extracted with diethyl ether, and
the ether was removed in vacuum to give a yellow viscous oil (189 mg),
which was identified by multinuclear NMR and HRMS as a mixture of
1
3
1
of two components, 4b and 10b (75:25% by H NMR integration of tBu
8
b and recovered 1b (d P=71.3ppm) in 62: 38 molar ratio based on
1
signals), which were characterized by NMR and HRMS (data for 10b are
3
H NMR integration of CMe protons (yield of 8b 70% relative to con-
1
in accordance with those below). Compound 4b: H NMR (C
6
D
6
): d=
verted 1b). (Addition of tBuLi can be ruled out by NMR reaction moni-
3
2
1
3 3
0.86 (s, 9H; CMe ), 0.96 (d, JP, H =12.0 Hz, 9H; PCMe ), 2.38 (d, J=
14.6 Hz, 1H; NCH ), 2.91 (d, J=14.6 Hz, 1H; NCH ), 3.16 (dd, J =
a b P, H
.3, J=13.1 Hz; PCHtrans to t-BuN), 3.59 (dd, J=13.0, JP, H =3.5 Hz, 1H;
PCHcisN), 6.44 (brd, J=8.2 Hz; H-7), 6.72 (ddd, J=7.3,
toring of the crude reaction mixture). Compound 8b. H NMR
2
2
4
(
4
[D
.40 (brs, 2H; NCH
perimposed with 1b; H-6), 7.79 (d, J=8.6 Hz, 1H; H-7), 7.96 ppm (m,
8
]THF): d=0.46 (d,
J
P, H =1.2 Hz, 9H; SiMe
3
), 0.96 (s, 9H; CMe
3
),
2
2
2
2
2
), 7.05 (m, superimposed with 1b; H-5), 7.27 (m, su-
3
3
4
4
3
J
P, H =2.3, J=
3
4
1
3
1
0.8 Hz, 1H; H-5), 7.20 (dd, J=8.5, J=1.5 Hz, 1H; H-6), 7.45 ppm (ddd,
superimposed with 1b; H-4); C{ H} (DEPT) NMR ([D
), 29.65 (s; CMe
0.84 (d, J=3.0 Hz; NCH
8
]THF): d=2.79
), 35.97 (d, J=1.6 Hz; CMe ),
), 116.06 (s; CH-7), 119.91 (d, J=11.5 Hz;
3
3
4
13
1
3
4
J=7.2,
d=27.35 (d, J=14.6 Hz; PCMe
PCMe ), 35.05 (s; CMe ), 53.85 (d, J=21.2 Hz; PCH
NCH ), 109.21 (s; CH-7), 117.87 (d, J=7.8 Hz; CH-6), 124.60 (d, J=
J
P,H =5.6, J=1.4 Hz, 1H, H-4); C{ H} (DEPT) NMR (C
6
D
6
):
), 30.80 (d, J=19.8 Hz;
N), 65.58 (s;
(
6
d,
J
P, H =9.1 Hz; SiMe
3
3
3
2
1
3
3
3 3
), 29.03(s; C Me
2
1
4
2
3
3
2
CH-5), 124.44 (d, J=2.8 Hz; CH-6), 128.88 (d, J=20.2 Hz; CH-4),
4
1
1
2
2
1
(
7
44.68 (d, J=43.1 Hz; C
q
31
-3a), 148.51 (d, J=4.0 Hz, C
q
-7a), 182.72 ppm
q 8
-2); P{ H} NMR ([D ]THF): d=126.67; MS (EI,
+
2
1
1
1.5 Hz;
57.96 ppm (s; C
q
C -3a), 131.34 (s; CH-5), 132.89 (d, J=21.9 Hz; CH-4),
1
1
d, J=75.0 Hz; C
0 eV, 1708C): m/z (%)=277 (23) [M] , 220 (39), 73 (100) [SiMe
HRMS (ESI in MeOH, NH OAc): m/z: calcd for C15 25NPSi: 278.14884
M+H] ; found: 278.14910. Experiments with smaller amounts of
3
1
1
q
-7a); P{ H} NMR (C
OAc): m/z: calcd for C16
found: 264.18765.
-tert-Butyl-1-(2,2-dimethyl-propyl)-2,3-dihydro-1H-1,3-benzazaphos-
6
D
6
): d=À8.95 ppm; HRMS (ESI
+
] ;
3
+
in MeOH, NH
4
H
27NP: 264.18756 [M+H] ;
4
H
+
[
3
KOtBu, from one to three equivalents relative to tBuLi, gave similar re-
phole-2-carboxylic acid (7b) and meso-3,3’-bis[2-tert-butyl-1-(2,2-dimeth-
yl-propyl)-2,3-dihydro-1H-1,3-benzazaphosphole] (10b): tBuLi (1.5m in
pentane, 0.50 mL, 0.75 mmol) was added dropwise at À308C to a solution
of 1b (127 mg, 0.62 mmol) in pentane (2 mL). This mixture was allowed
to warm slowly to room temperature and stirred overnight. The resulting
sults.
Lithiation of 1c in diethyl ether: tBuLi (1.7m pentane solution, 0.13mL,
0
.22 mmol) was added at À608C to 1c (50 mg, 0.19 mmol) in Et
2
O
(
2 mL), the mixture was stirred at room temperature overnight, and the
3
1
1
8
solvent was replaced with [D ]THF. P{ H} NMR displayed a major peak
orange-yellow solution was cooled to À608C, and gaseous CO
ice) was introduced over a period of 90 min, leading to a color change
from orange to yellow. A slight excess of Me SiCl (0.09 mL, 0.74 mmol)
2
(from dry
at d=À21.9 ppm (4c) and two small peaks at d=À14.9 ppm (3c, uncer-
tain) and d=101 ppm (broadened, 2c). The lack (or low intensity) of a
3
PCH(Li)N resonance and the occurrence of a PCH
2
N signal in the
was then added at the same temperature, and the mixture was stirred at
room temperature for 6 h (colorless). Insoluble material was filtered off
and washed thoroughly with ether. Removal of the solvent gave a color-
less semicrystalline substance, which was treated with dry MeOH (5 mL).
Removal of volatiles in vacuum provided a viscous oil, which solidified
on cooling and was recrystallized from saturated MeOH solution to give
colorless 7b (130 mg, 68%). Single crystals of 11b, identified by X-ray
crystal structure analysis as meso-11b, were grown by slow diffusion of
aerial oxygen into the mother liquor containing the side product 10b.
1
3
1
C{ H} (DEPT) NMR spectrum hint at the protonation of 3c to 4c
1
3
1
within about 15 h (overnight). Compound 4c: C{ H} (DEPT) NMR: d=
2
1
2
6.70 (d, J=14.3Hz; PC Me
3
), 30.81 (d, J=20.4 Hz; PCMe
), 44.26 (small d, J=18.4 Hz; PCH
3
), 31.01
N),
1
(
CH), 37.34 (CH ), 39.91 (CH
2
2
2
1
3
5
8
6.21 (NC
.5 Hz; C
-7a).
-Adamantan-1-yl-3-tert-butyl-2,3-dihydro-1H-1,3-benzazaphosphole-2-
q
), 112.26 (CH-7), 116.05 (d, J=8.5 Hz; CH-5), 126.23(d, J=
-3a), 129.98 (CH-6), 133.37 (d, J=24.0 Hz; CH-4), 153.55 ppm
2
q
(
s; C
q
1
1
3
carboxylic acid (7c): tBuLi (1.5m in pentane, 0.33 mL, 0.50 mmol) was
added dropwise at À608C to a solution of 1c (123mg, 0.46 mmol) in di-
ethyl ether (2 mL). This mixture was allowed to warm slowly to room
3 3
H NMR (CD OD): d=1.01 (s, 9H; CMe ), 1.03(d, JP, H =12.0 Hz, 9H;
2
4
2
PCMe ), 2.78 (dd, J=15.3, J =2.0 Hz, 1H; NCH ), 3.33 (dd, J=15.9,
3
P, H
A
4
2
J
P, H ꢀ2 Hz, 1H; NCH
B
), 4.54 (d, JP, H =2.7 Hz, 1H; PCHcisN), 6.59 (brd,
Chem. Eur. J. 2008, 14, 4328 – 4335
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4333

J. Heinicke et al.
3
3
4
4
3
J=8.4 Hz, 1H; H-7), 6.66 (tdd, J=7.2, JP,H =2.4, J=0.6 Hz, 1H; H-5),
(C
6
D
6
): d=0.57 (s, 9H; SiMe
3
), 0.89 (s, 9H; CMe
3
), 1.48 (d,
J
P, H
=
3
4
3
3
7
.20 (td, J=8.4, ꢀ7, J=1.5 Hz, 1H; H-6), 7.24 (ddd, J=7.2, JP, H =6.0,
13.9 Hz, 9H; PCMe
CH
3
), 1.50–1.80 (brm, 4H; CH
2
), 2.00–2.40 (brm, 4H;
4
+
13
1
2
2
4
J=1.5 Hz, 1H; H-4), NH with solvent OH at 4.96 ppm; C{ H}
2
), 2.91 (d, J=14.7 Hz, 1H; NCH
), 4.18 (m br, 1H; =CH), 4.49 (brm, 1H; =CH), 4.54 (d,
JP, H =10.8 Hz, 1H; PCHN), 5.42 (brm, 1H; =CH), 5.71 (brm, 1H; =
A
), 3.15 (d, J=14.7, JP, H =1.8 Hz,
2
(
DEPT) NMR (CD
3
OD): d=26.93(d, J=15.8 Hz; PCMe
), 31.95 (d, J=22.6 Hz; PCMe ), 35.33 (s; CMe ), 62.09 (s; NCH
7.39 (d, J=25.7 Hz; PCHN), 109.41 (s; CH-7), 117.88 (d, J=8.1 Hz;
3
), 28.74 (s;
1H; NCH
B
1
2
CMe
6
3
3
3
2
),
1
4
3
3
4
4
CH), 6.36 (brd, J=8.3Hz, 1H; H-7), 6.53(ddd, J=7.2, JP, H =2.7, J=
0.9 Hz, 1H; H-5), 7.10, 7.12 ppm (superimposed m, 2H; H-6, H-4);
1
2
CH-6), 122.25 (d, J=11.8 Hz; C
q
-3a), 131.57 (s; CH-5), 132.31 (d, J=
2
13
1
3
2
3.1 Hz; CH-4), 157.87 (s; C
q
-7a), 176.77 ppm (d, J=14.1 Hz; CO);
OD): d=19.50 ppm; MS (EI, 70 eV, 1208C): m/z (%): 309
C{ H} (DEPT) NMR (C
J=2.0 Hz; CH
(brs; CH ), 33.31 (brs; CH
6
D
6
): d=5.52 (d, J=3.9 Hz; 2-SiMe
3
), 28.35 (d,
), 30.20
), 35.74 (s; CMe ),
3
1
2
P NMR (CD
3
2
), 29.05 (s; CMe
3
), 30.87 (d, J=6.4 Hz; PCMe
3
+
+
(
4
2) [M+1] , 308 (9) [M] , 264 (11), 223(16), 207 (57), 1 36 (40), 57 (100),
1 (72); HRMS (EI, 70 eV): m/z: calcd for C17 P 307.17012;
found: 307.1693.
-tert-Butyl-1-(2,2-dimethylpropyl)-2-trimethylsilyl-2,3-dihydro-1H-1,3-
2
1
2
), 34.62 (d, J=3.9 Hz; CH
2
3
1
3
H
26NO
2
38.77 (d, J=6.6 Hz; PCMe
4.1 Hz; NCH
CH=), 101.39 (dd, JRh,C =7.8, J=14.5 Hz; CH=), 104.04 (dd, JRh,C =7.8,
3
), 57.70 (d, J=5.1 Hz; PCH), 63.31 (d, J=
2
), 65.29 (d, JRh,C =13.6 Hz; CH=), 70.84 (d, JRh,C =13.4 Hz;
3
3
3
J=11.3Hz; CH =), 109.46 (d, J=4.0 Hz; CH-7), 117.47 (d, J=9.2 Hz,
CH-5), 118.13(dd, J=28.4 Hz; C -3a), 131.57 (d, J=9.2 Hz; CH-4),
q
benzazaphosphole ((E)-9b) and 2-tert-butyl-1-(2,2-dimethylpropyl)-2,3-
dihydro-1H-1,3-benzazaphosphole ((E/Z)-10b): tBuLi (1.5m in pentane,
0
0
1
2
3
1
1
1
32.59 (brs; CH-6), 157.29 ppm (s; C
q
-7a); P{ H} NMR (C
6
D
6
): d=
.14 mL, 0.21 mmol) was added dropwise at À308C to 1b (35 mg,
1
3
3.54 ppm
(d,
J
Rh,P =150.7 Hz);
HRMS (ESI): calcd
for
.17 mmol) in pentane (1 mL). This mixture was allowed to warm slowly
+
C
27
H
46ClNPRhSi: 546.21872 [MÀCl] ; found: 546.21867 (strong tendency
to room temperature and stirred for 20 h. The reaction flask was again
SiCl (0.03mL, 0.2 36 mmol) was added dropwise,
to formation of Rh clusters observed in ESI HRMS measurements).
cooled to À608C, Me
3
and the mixture was stirred at room temperature overnight. Insoluble
material was filtered off and washed thoroughly with pentane. The sol-
vent was removed under vacuum to give a colorless oil (50 mg) consisting
Compound 4b as a ligand in palladium-catalyzed C–N coupling of 2-bro-
mopyridine with mesitylamine: Toluene (5 mL) was placed in an oven-
dried Schlenk vessel charged with 2-bromopyridine, 2,4,6-trimethylani-
1
of two components, (E)-9b and (E/Z)-10b (80:20 by H NMR integration
2 3
line, palladium acetate or Pd (dba) , 4b, and NaOtBu (amounts see
A
H
R
U
G
of tBu signals), which were characterized by NMR and mass spectroscop-
ic data. Compound (E)-9b exists as only one pair of diastereoisomers,
while (E/Z)-10b forms a major and a minor pair of diastereoisomers, in-
dicated by two P signals and two sets of similar proton signals (partly
superimposed).
Table 2). The resulting deep red-brown mixture was heated for 48 h at
3
1
Table 2. Pd-catalyzed coupling of 2-bromopyridine with 2,4,6-trimethyl-
A
H
R
U
G
1
4
Compound (E)-9b: H NMR (C
6
D
6
3
): d=0.12 (d,
J
P, H =1.5 Hz, 9H;
2-Bromopyri-
dine [g
(mmol)]
Mes-NH
[g
(mmol)]
2
Pd source
[mg
(mol%)]
Ligand
[mg
(mol%)] (mmol)]
NaOtBu
[mg
Yield
[mg
(%)]
SiMe
3
), 0.94 (s, 9H; CMe
J=14.9 Hz, 1H; NCH
P, H =4.6 Hz, 1H; PCHcisN), 6.36 (brd, J=8.3Hz, 1H; H-7), 6.64 (ddd,
P, H =2.5, J=0.9 Hz, 1H; H-5), 7.16 (ddd, J=8.3, 7.2, J=
.5 Hz, 1H; H-6), 7.42 ppm (ddd, J=7.2,
3
), 1.01 (d, JP, H =12.1 Hz, 9H; PCMe
), 3.16 (d, J=14.9 Hz, 1H; NCH
3
), 3.05 (d,
2
2
a
b
), 3.76 (d,
2
3
3
J
0.32 (2.0)
0.16 (1.0)
0.16 (1.0)
0.325
Pd
2.2 (0.5)
Pd(OAc)
11 (5.0)
[Pd (dba)
46 (5.0)
A
T
E
N
(OAc)
2
5 (1.0)
13(5.0)
20 (7.5)
27 (2.8)
1 34 (1.4)
134 (1.4)
180
(13)
65
(29)
120
4
4
3
4
J=7.2,
J
(
2.4)
0.162
1.2)
0.162
1.2)
3
3
4
1
4
(
J
P, H =5.7, J=1.5 Hz, 1H; H-
): d=0.68 (d, J=9.3Hz; 2-SiMe
A
H
R
U
G
2
1
3
1
3
); C{ H} (DEPT) NMR (C
6
D
6
3
), 27.38
),
), 107.9 (s;
-3a),
-7a);
): d=À1.70 ppm; HRMS: m/z: calcd for (E)-9b
34NPSi: 336.22709; found: 336.22712.
(
2
1
d, J=15.7 Hz; PCMe
3
), 29.22 (s; CMe
3
), 31.98 (d, J=27.9 Hz; PCMe
3
A
H
R
U
G
2
A
T
E
G
3
]
1
3
6.24 (s; CMe
3
), 54.63(d, J=39.8 Hz; PCHN), 60.81 (s; NCH
2
(
(53)
4
1
CH-7), 116.68 (d, J=8.0 Hz; CH-6), 123.09 (d, J=10.7 Hz; C
q
2
1
31.36 (s; CH-5), 132.85 (d, J=23.7 Hz; CH-4), 156.91 ppm (s; C
q
3
1
1
6 6
P{ H} NMR (C D
1
008C and was then allowed to cool to room temperature, and diethyl
C
19
H
ether (5 mL) was added. The resulting mixture was washed with brine,
and the organic layer was dried over Na SO and concentrated in
vacuum. The remaining yellow oily product was purified by column chro-
matography on silica gel with ethyl acetate/hexane (10%) as eluent to
give pure 2-mesitylaminopyridine as a colorless solid. NMR data are in
accordance with reported values.
Compound 7b as a ligand in nickel-catalyzed ethylene oligomerization:
Compound 7b (20.0 mg, 65 mmol) and Ni(COD) (17.9 mg, 65 mmol)
were dissolved in toluene (each in 10 mL) and mixed at room tempera-
ture. The resulting orange-yellow solution was stirred at room tempera-
ture for 30 min and transferred into an argon-filled stainless steel auto-
clave (75 mL). The autoclave was pressurized (ca. 50 bar) with ethylene
(12.3g) and put in a silicon oil bath. After heating for ca. 15 h at 70 8C,
cooling to room temperature, and weight measurement, unconverted eth-
ylene (together with some butenes) was released through a cooling trap
(À708C, no liquid condensate). The polymer with solvent and oligomers
was then transferred to a flask, and all volatiles were flash-distilled at 3–
1
Compound (E/Z)-10b: H NMR (C
6
D
6
): d=0.81, 0.88 (2 s; CMe
), 3.55 (d, J=15.2 Hz, 1H;
P, H =1.7 Hz, 1H; PCHN), 4.45 (ddt,
3
, 2-
2
2
2
4
CMe
NCH
1
3
), 2.97 (d, J=15.2 Hz, 1H; NCH
), 3.72 (dd, J=7.1,
83, J=7.1, J+J’=2.3Hz, 1H; P,H), 6.42 (brd, J=8.3Hz; H-7), 6.59
ddd, J=7.2, JP, H =2.3, J=0.9 Hz, 1H; H-5), 7.07 (tt, J=8.3, 7.2,
A
3
2
1
B
3
J
J
P, H
=
4
3
3
4
4
3
(
[
19]
4
J+J’=2–3Hz, 1H; H-4 or H-6); less intense diastereoisomer: 0.8 3, 0.89
2
2
(
1
2 s; CMe
5.3Hz, 1H; NCH
3
, 2-CMe
3
), 2.90 (d, J=15.3Hz, 1H; NCH
), 4.04 (brd, JP, H =33 Hz, PCHN, uncertain), 4.42 (su-
JP, H =194, J+J’=4.5 Hz; PH, uncertain), 6.43(d; H-7),
.71 (tm; H-5), 6.60 ppm (tm; H-4 or H-6); H-6 or H-4 superimposed;
C{ H} (DEPT) NMR (C
s; CMe ), 37.02 (s; CMe
2
), 71.92 (d, J=12.0 Hz; PCHN), 110.45 (s; CH-7), 117.79 (d, J=
.0 Hz; CH-6), 120.15 (d, J=4.6 Hz; C
a
), 3.45 (d, J=
2
ACHTREUNG
2
b
1
perimposed ddt,
6
1
3
1
3
6
D
6
): d=28.24 (d, J=10.4 Hz; 2-CMe
), 39.83 (d, J=19.0 Hz; 2-CMe
3
), 29.70
2
(
3
3
3
), 61.12 (s;
1
4
NCH
1
9
q
-3a), 130.56 (s; CH-5), 132.09 (d,
-7a); minor diastereoisomer not
): d=À82.28, À66.35 ppm,
2
J=25.1 Hz; CH-4), 156.67 ppm (s; C
detectable in C NMR; P{ H} NMR (C
intensity ratio 80:20%.
q
1
3
31
1
6 6
D
4
mbar/70–808C into a cooling trap (À1968C) and analyzed by GC (total
Rhodium(h-P-3-tert-butyl-1-(2,2-dimethylpropyl)-2-trimethylsilyl-2,3-di-
hydro-1H-1,3-benzazaphosphole)(1,5-cyclooctadiene) chloride (12b):
of oligomers 0.6 g, of which 0.07 g butenes, 0.13g hex-1-ene, 0.14 g oct-1-
ene, 0.08 g dec-1-ene, small amounts of other olefins). The residual poly-
mer was extracted with a mixture of methanol and concentrated hydro-
chloric acid (each 25 mL) by stirring overnight at room temperature, and
was then washed with methanol and dried in vacuum, yielding waxy PE
(11.0 g), m.p. 115–1178C, 1 0.91 gcm
1108C after swelling for 1 d at 1208C; more details see earlier report
integration ratios of vinyl, alkene, CH , and CH indicate 78/22% a-ole-
fins, 1.6 Me/Vin, 30 Me/1000 C, MNMR 725 gmol . The conversion was=
[
(
Rh
A
C
H
T
R
E
U
N
G
(cod)Cl]
2
(29 mg, 0.06 mmol) was added at À308C to the mixture of
E)-9b and (E/Z)-10b (40 mg, 0.12 mmol) dissolved in THF (1 mL), and
the mixture was stirred at room temperature for 5 d. THF was partly re-
moved, and the solution was overlayered with n-hexane to give colorless
crystals of 12b. A crystal taken from the mixture with the mother liquor
was analyzed by X-ray diffraction and found to be a THF hemisolvate
À3
1
6 5
. H NMR (in C D Br at 100–
[
21a]
)
(
crystal data see Table 1). The crystals were then separated, washed with
2
3
1
À1
hexane, dried (60 mg, 87%), and characterized by NMR. H NMR
4334
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 4328 – 4335

Novel Heterocyclic P- and P,O-Ligands
FULL PAPER
1
6
1.6 g (=94%, oligomers in MeOH/HCl extract not determined), TON=
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[22]
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Acknowledgements
Financial support and a fellowship (B.R.A.) from the Deutsche For-
schungsgemeinschaft are gratefully acknowledged. We thank B. Witt for
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Sommer-Udvarnoki (Georg-August-Universität Gçttingen, Institut für
Organische und Biomolekulare Chemie) for HRMS measurements.
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Received: December 20, 2007
Published online: March 25, 2008
Chem. Eur. J. 2008, 14, 4328 – 4335
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4335