Kloning Manusia

In the last few years, very rapid progress in the cloning technology and its development towards human cloning has become a hotly-debated issue. Cloning, which is the process of formation of a number of individuals with the same genetic structure, can be done by means of embryo-splitting method and nuclear transfer. Human cloning through the nuclear transfer method is directed towards two purposes, i.e. reproduction and therapy. The relatively new transgenic technology can be combined with the cloning technique to produce clones with new genes. However, pros and cons arise concerning the development of research on human cloning, particularly cloning for reproductive purposes. Therefore, there is need for a moratorium period before human cloning can be performed in order that solutions for all kinds of problems related to safety and ethics can be found

A New High-Yield Synthesis of Cl₃PNSiMe₃, a Monomeric Precursor for the Controlled Preparation of High Molecular Weight Polyphosphazenes

The phosphoranimine, Cl3PNSiMe3, was prepared using a new, high-yield (>80%), one-pot synthesis via oxidation of the chlorophosphine, Cl2PN(SiMe3)2 with SO2Cl2 in ether. Cl3PNSiMe3 is a valuable monomeric precursor in the synthesis of well-defined polyphosphazenes

A New, Convenient Synthesis of the Linear Phosphazene Salt [Cl₃PNPCl₃]Cl: Preparation of Higher Linear Homologues [Cl₃PN−(PCl₂N)<i>_x</i>PCl₃]Cl (<i>x</i> = 1−3) and the 16-Membered Macrocycle [NCCl(NPCl₂)₃]₂

An improved synthetic route to the linear phosphazene salt [Cl3PNPCl3]Cl is reported. This species is a useful precursor to higher linear homologues and also to heterocycles such as the 16-membered carbophosphazene macrocycle [NCCl(NPCl2)3]2

A New, Convenient Synthesis of the Linear Phosphazene Salt [Cl₃PNPCl₃]Cl: Preparation of Higher Linear Homologues [Cl₃PN−(PCl₂N)<i>_x</i>PCl₃]Cl (<i>x</i> = 1−3) and the 16-Membered Macrocycle [NCCl(NPCl₂)₃]₂

An improved synthetic route to the linear phosphazene salt [Cl3PNPCl3]Cl is reported. This species is a useful precursor to higher linear homologues and also to heterocycles such as the 16-membered carbophosphazene macrocycle [NCCl(NPCl2)3]2

Carbene-Bound Borane and Silane Adducts: A Comprehensive DFT Study on Their Stability and Propensity for Hydride-Mediated Ring Expansion

The stability of a variety of borane (BH₃ and BH₂NHMe) and silane (SiH_<i>n</i>Ph_4–<i>n</i>, <i>n</i> = 0–4) adducts with diamino (NHC) and aminoalkyl (CAAC) carbenes has been carefully examined using M06-2X/cc-pVDZ computations, including natural bond orbital and atoms-in-molecules analyses. Moreover a potential mechanism for the hydride-mediated ring expansion of the carbene donors is reported. While the NHC adducts can undergo thermally induced ring-expansion chemistry, the CAAC adducts show increased stability due to a large energetic barrier for the insertion of boron (or silicon) atoms into the CAAC heterocycle. A series of substituted NHCs were investigated to further explore the roles of both electronic and steric effects on adduct stabilities and on their propensities for undergoing ring-expansion transformations

Zinc-Mediated Transmetalation as a Route to Anionic <i>N</i>‑Heterocyclic Olefin Complexes in the p‑Block

Anionic N-heterocyclic olefins (aNHOs) are suited well for the stabilization of low-coordinate inorganic complexes, due to their steric tunability and strong σ- and π-electron donating abilities. In this study, the new two-coordinate zinc complex (MeIPrCH)2Zn (MeIPrCH = [(MeCNDipp)2CCH]−, Dipp = 2,6-diisopropylphenyl) is shown to participate in a broad range of metathesis reactions with main group element-based halides and hydrides. In the case of the group 14 halides, Cl2E·dioxane (E = Ge and Sn), transmetalation occurs to form dinuclear propellane-shaped cations, [(MeIPrCHE)2(μ-Cl)]+, while the aNHO-capped phosphine ligand MeIPrCH-PPh2 is obtained when (MeIPrCH)2Zn is combined with ClPPh2. Lastly, ZnH2 elimination drives transmetalation between (MeIPrCH)2Zn and hydroboranes and hydroalumanes, leading to Lewis acidic aNHO-supported -boryl and -alane products

Interaction of Carbene and Olefin Donors with [Cl₂PN]₃: Exploration of a Reductive Pathway toward (PN)₃

The iminophosphine–phosphazene [PIII–PV] heterocyclic adduct [IPr·PN(PCl2N)2] was prepared via reduction of the cyclic phosphazene [Cl2PN]3 in the presence of the carbene donor IPr {IPr = [(HCNDipp)2C:], where Dipp = 2,6-iPr2C6H3}. By contrast, the treatment of [Cl2PN]3 with the N-heterocyclic olefin IPrCH2 yielded the olefin-grafted phosphazene ring [(IPrCH)P(Cl)N(PCl2N)2]

Zinc-Mediated Transmetalation as a Route to Anionic <i>N</i>‑Heterocyclic Olefin Complexes in the p‑Block

Anionic N-heterocyclic olefins (aNHOs) are suited well for the stabilization of low-coordinate inorganic complexes, due to their steric tunability and strong σ- and π-electron donating abilities. In this study, the new two-coordinate zinc complex (MeIPrCH)2Zn (MeIPrCH = [(MeCNDipp)2CCH]−, Dipp = 2,6-diisopropylphenyl) is shown to participate in a broad range of metathesis reactions with main group element-based halides and hydrides. In the case of the group 14 halides, Cl2E·dioxane (E = Ge and Sn), transmetalation occurs to form dinuclear propellane-shaped cations, [(MeIPrCHE)2(μ-Cl)]+, while the aNHO-capped phosphine ligand MeIPrCH-PPh2 is obtained when (MeIPrCH)2Zn is combined with ClPPh2. Lastly, ZnH2 elimination drives transmetalation between (MeIPrCH)2Zn and hydroboranes and hydroalumanes, leading to Lewis acidic aNHO-supported -boryl and -alane products

Donor-Stabilized Cations and Imine Transfer from <i>N</i>-Silylphosphoranimines

A series of donor-stabilized N-silylphosphoranimine salts [DMAP·PCl2NSiMe3]+X- (DMAP = 4-(dimethylamino)pyridine) were prepared by the reaction of Cl3PNSiMe3 with DMAP in the presence of silver salts AgX (X = OSO2CF3, BF4, and SbF6). Repeating the reaction in the absence of AgX gave the chloride salt [DMAP·PCl2NSiMe3]Cl which has been shown to be in equilibrium with free DMAP and Cl3PNSiMe3. Attempts to stabilize a N-silylphosphoranimine cation with phosphine donors led to unexpected imine transfer chemistry. For example, Cl3PNSiMe3 reacts with phosphines, R3P (R = nBu and Ph), to produce the metathesis products PCl3 and R3PNSiMe3 which subsequently react together to afford the N-phosphinophosphoranimines R3PN−PCl2 and ClSiMe3 as a byproduct

Synthesis and Characterization of New Nitrogen-Donor-Stabilized <i>N</i>-Silylphosphoranimine Cations

The phosphoranimine Br(CF3CH2O)2PNSiMe3 (12) reacts quantitatively with nitrogen bases pyridine, 4,4‘-bipyridine, and quinuclidine (quin) to form the N-donor stabilized phosphoranimine cations [N-donor·P(OCH2CF3)2NSiMe3] ([15]+) in the presence of the halide abstractor AgOTf. In contrast to quinuclidine, in the absence of a halide abstractor, the weak bases pyridine and 4,4‘-bipyridine do not undergo reactions with 12 or with the phosphoranimine Cl3PNSiMe3 (7). Furthermore, unlike the weaker bases, quinuclidine also reacts with 7 to form the expected quinuclidine-stabilized phosphoranimine cation [quin·PCl2NSiMe3]+ ([16]+) in the presence of AgOTf. However, in the absence of AgOTf, quinuclidine reacts with 7 to presumably yield the salt [16]Cl, which then undergoes a further quinuclidine ring-opening reaction to yield the cationic piperidyl-substituted phosphoranimine [(quin)CH2CH2C5H9N−PCl2NSiMe3]Cl ([19]Cl). Reactions involving 7 and 12 with other halide abstraction reagents, such as GaCl3, are also described