Direct heating of a metal-organic framework provides a simple, controllable way of effecting a covalent post-synthetic modification. Herein we report that an allyloxy-tagged zinc metal-organic ...framework undergoes a thermally-promoted aromatic Claisen rearrangement through which the framework connectivity and porosity are maintained.
Post-synthetic rearrangements of a bridging ligand are effected by simply heating the metal-organic framework.
Herein we report the synthesis and characterisation of a series of Zr(
iv
) 2,2′-bipyrrolidine-salan derived complexes and their exploitation for the ring opening polymerisation of
rac
-lactide to ...afford highly isotactically enriched polymers.
We report a series of Zr(
iv
) 2,2′-bipyrrolidine-salan derived complexes and their exploitation for the ROP of
rac
-lactide to afford highly isotactically enriched PLA.
The chemistry of
N
-organosilylalkyl-substituted heterocyclic bases (thymine, adenine and cytosine) is described, covering the structures of model compounds, the synthesis of substituted ...oligo-siloxanes and a preliminary report of the synthesis of a poly(organosiloxane) with pendant
N
-alkyl(heterocycle) functionalities.
N
-Alkenylthymines CH
2
&z.dbd;CH(CH
2
)
n
T (T = thymine,
n
= 1 (
1
), 2 (
2
), 3 (
3
)) have been prepared and
2
hydrosilylated to form PhMe
2
Si(CH
2
)
4
T (
5
). Alternatively,
5
was prepared by reaction of PhMe
2
Si(CH
2
)
4
Br (
6
) with (
O
,
O
-SiMe
3
)
2
T, a method which has also been used to prepare PhMe
2
Si(CH
2
)
4
A (
7
) and PhMe
2
Si(CH
2
)
4
C (
8
) (A = adenine, C = cytosine). Model di- and tri-siloxanes Br(CH
2
)
4
(Me)
2
Si
2
O (
10
), Me
3
SiOSi(Me)
2
(CH
2
)
4
Br (
11
), PhMe
2
SiOSi(Me)
2
(CH
2
)
4
Br (
12
) and (Me
3
SiO)
2
(Me)Si(CH
2
)
4
Br (
13
) have been prepared by hydrosilylation of H
2
C&z.dbd;C(H)(CH
2
)
4
Br with an appropriate hydrosiloxane and used to prepare Me
3
SiO(Me)
2
Si(CH
2
)
4
T (
14
), Me
3
SiO(Me)
2
Si(CH
2
)
4
A (
15
) (both from
11
), and (Me
3
SiO)
2
(Me)Si(CH
2
)
4
T (
16
), (Me
3
SiO)
2
(Me)Si(CH
2
)
4
A (
17
) (both from
13
).
10
reacts with thymine to give a mixture of the pyrimidocyclophane
cyclo
-T-
N
,
N
-(CH
2
)
4
(Me)
2
Si
2
O (
19
) and T(CH
2
)
4
Si(Me)
2
2
O (
20
), while cytosine reacts similarly to form
cyclo
-C-
N
,
N
-(CH
2
)
4
(Me)
2
Si
2
O (
21
; as an imine) and C(CH
2
)
4
Si(Me)
2
2
O (
22
); adenine only generates A(CH
2
)
4
Si(Me)
2
2
O (
18
) in an analogous synthesis. Using a related protocol, polymeric {MeSi(O)(CH
2
)
4
Br
2
Me
2
SiO
98
}
n
(
23
) has been converted to {MeSi(O)(CH
2
)
4
T
2
Me
2
SiO
98
}
n
(
24
) and {MeSi(O)(CH
2
)
4
A
2
Me
2
SiO
98
}
n
(
25
). The structures of
4
,
5
,
8
,
19
and
21
, along with a 2 : 1 adduct of
5
with Ni(dithiobiuret)
2
(
9
) are reported.
Model organosilicon derivatives of DNA bases and polymeric analogues are reported with the crystallographically studied formation of hydrogen-bonded aggregates.
The structure of the first tetrameric α-lithiated N-phenylphosphazene has been determined in the solid state and shown to persist in toluene solution, an observation that gives insight into the ...variation in stereoselectivity found for reactions of α-lithiated phosphazenes with aldehydes.
Biooxidation of benzoic acid by Ralstonia eutropha B9 provides an unusual cyclohexadiene carboxy diol that contains a quaternary stereocentre. Tricarbonyliron derivatives of this chiron, on treatment ...with acid, give two isomeric η5-cyclohexadienyl complexes as observed by NMR spectroscopy. Both of these can be subjected to the addition of nucleophiles to provide isomeric cyclohexadiene complexes with new substituent patterns, several of which have been characterised crystallographically. De-metallation of these provides a versatile library of cyclohexadiene building blocks, the utility of which is demonstrated by formal syntheses of oseltamivir. The mechanism of product formation and its stereochemical implications are discussed, as are the procedures undertaken to establish the enantiopurity of a representative cyclohexadiene product. PUBLICATION ABSTRACT
Abstract
Biooxidation of benzoic acid by
Ralstonia eutropha B9
provides an unusual cyclohexadiene carboxy diol that contains a quaternary stereocentre. Tricarbonyliron derivatives of this chiron, on ...treatment with acid, give two isomeric η
5
‐cyclohexadienyl complexes as observed by NMR spectroscopy. Both of these can be subjected to the addition of nucleophiles to provide isomeric cyclohexadiene complexes with new substituent patterns, several of which have been characterised crystallographically. De‐metallation of these provides a versatile library of cyclohexadiene building blocks, the utility of which is demonstrated by formal syntheses of oseltamivir. The mechanism of product formation and its stereochemical implications are discussed, as are the procedures undertaken to establish the enantiopurity of a representative cyclohexadiene product.
Lithiation of 2,6-di-
tert-butyl-4-methylphenol in toluene in the presence of Ph
2P(O)N(CH
2Ph)CH
3 leads to a lithium aryloxide dimer consisting of a Li
2O
2 four-membered ring with each lithium ...atom is coordinated to a phosphinamide. The structure found in the solid state by X-ray crystallography is retained in toluene solution as determined by multinuclear NMR spectroscopy. The new complex described gives insight into the mechanism of lithiation of phosphinamides.
The addition of LiBu
n
to a toluene solution of Ph
2P(O)N(CH
2Ph)CH
3
1 and 2,6-di-
tert-butyl-4-methylphenol
5 leads to the formation of the mixed dimer (Ph
2P(O)N(CH
2Ph)CH
3)
·
LiOC
6H
2-2,6-{C(CH
3)
3}
2-4-CH
3)
·
C
7H
8
2
6. The single crystal X-ray structure shows that two lithium aryloxide moieties dimerize giving rise to a Li
2O
2 core in which each lithium atom is additionally coordinated to a phosphinamide
1 ligand. The multinuclear magnetic resonance study (
1H,
7Li,
13C,
31P) indicates that the solid-state structure is preserved in toluene solution. Complex
6 may be considered as a model for the pre-complexation step preceding the metalation of phosphinamides by an organolithium base.
Reaction of GeCl4 and CyPH2 leads to a range of products from which crystals of CyPH3+GeCl3- have been obtained. The major intermediate in this reaction, Cy(H)PGeCl3, can be obtained as the dominant ...product only when an excess of GeCl4 is used in the preparation. Similarly, crystals of Ph2PH2+GeCl3- have been obtained from reaction of Ph2PH and GeCl4(1 : 1). The structures of both primary and secondary phosphonium cations are reported. Aerosol-assisted and low-pressure chemical vapour deposition experiments using Cy(H)PGeCl3 as precursor lead to the deposition of thin films containing both germanium and phosphorus, contaminated with large amounts of oxygen. GeP has been identified as components of the film from bandgap measurements.
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