Desymmetrization of 4,6-diprotected myo-inositol

The asymmetric desymmetrization of 4,6-diprotected myo-inositol derivatives was achieved by using a bifunctional, readily available nucleophilic catalyst. The orthogonally protected products were obtained in 80-99% yield with 90-99% ee. Such structures serve as potential enantiopure building blocks for the synthesis of myo-inositol phosphates.

Catalytic metal-free Si-N cross-dehydrocoupling

The metal-free B(C6F5)3 catalyzed dehydrocoupling of hydrosilanes with anilines, carbazoles and indoles is reported. For anilines and carbazoles the reaction proceeds by the liberation of H2 as the sole Si-N coupling byproduct. Indoles react with diphenyl(methyl) hydrosilane to give N-silyl indolines with high diastereoselectivity (d.r. 10 : 1) in excellent yields. A mechanism for this Si-N coupling/hydrogenation sequence is proposed.

Paracyclophane derivatives in frustrated Lewis pair chemistry

The metal-free activation of hydrogen was achieved using [2.2]paracyclophane-derived bisphosphines as Lewis base in frustrated Lewis pair chemistry. The rigid scaffold allows the orientation of functional groups so that steric aspects can be studied without altering the electronic nature. Depending on the geometry, structurally different phosphonium hydridoborates were generated when the frustrated Lewis pairs were exposed to hydrogen. The bisphosphines were applied in the 1,4-hydrosilylation-hydrogenation domino reaction providing access to secondary silyl-protected alcohols from enones in one step. Additionally, the planar-chiral scaffold was applied for the synthesis of novel enantiopure Lewis acids and Lewis bases.

Coupling of ortho-substituted aryl chlorides with bulky amides

Voluminous amides were coupled with deactivated, sterically hindered aryl chlorides in excellent yields providing products, which have not been efficiently accessible by transition metal catalysis so far. Application of an unsymmetric bisphosphine ligand was critical for the high catalytic activity.

Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

Bis(1-methylethenyl-cyclopentadienyl)zirconium dichloride (7a) was prepared by a fulvene route. Photolysis at 0 degrees C with Pyrex-filtered UV light resulted in a rapid and complete intramolecular [2+2]cycloaddition reaction to yield the corresponding cyclobutylene-bridged ansa-zirconocene dichloride isomer (8a). This is one of the rare examples of an organic functional group chemistry that leads to carbon-carbon coupling at the framework of an intact sensitive group 4 bent metallocene complex. More sterically hindered open metallocenes that bear bulky isopropyl or tert-butyl substituents at their Cp rings in addition to the active 1-methylethenyl functional group undergo the photochemical ansa-metallocene ring closure reaction equally facile. The metallocene systems used and obtained in this study have served as transition metal components for the generation of active metallocene propene polymerization catalysts.

Photogeneration of titanium(III) from titanium(IV) citrate in aqueous solution

Current interest in the biochemistry of Ti(IV) arises from its widespread use in white pigments and its potential in therapeutic agents. Citrate is known to form strong complexes with Ti(IV). We show here that Ti(III) citrate is generated in a facile manner and in good yield by the action of UV radiation on Ti(IV) citrate in aqueous solution. The Ti(III)-citrate species formed was isolated and characterised by UV-Visible spectroscopy, showing an absorption at 547 nm (epsilon=100 M(-1)cm(-1)), and by electron paramagnetic resonance (EPR) spectroscopy giving a resonance at g=1.949 (linewidth=60G) . An X-ray structure of the parent Ti(IV) complex in the form [TiNa(3)(C(6)H(6)O(7))(2)(C(6)H(5)O(7))(H(2)O)(6.8)].2H(2)O is reported along with a study of the reaction of Ti(IV)-citrate with N,N-ethylenebis(o-hydroxytoluene)glycine (EHTG), which was more rapid than those of other related Ti(IV) complexes.

Bilateral breast cancer. Risk reduction by contralateral biopsy

Although survival from primary breast cancer has improved with earlier diagnosis and treatment, the management of the opposite breast is still in question. The risk factors for bilaterality are known, and preoperative mammography is occasionally helpful, but identification of early second breast cancer is very limited. Contralateral biopsy may provide a reasonable answer to the problem. During a 5-year period, 62 elective contralateral biopsies were performed in patients having mastectomies for primary breast cancer. This consisted of either a mirror image biopsy or, more commonly, a biopsy of the upper outer quadrant. Thirteen patients had simultaneous contralateral cancers, of whom two had clinically overt bilateral cancers and 11 (18%) had clinically occult malignancy. Seven of these 11 had both radiologically and clinically normal breasts. Thus, 11.3% had radiologically and clinically occult cancer demonstrated by biopsy. Surgical management consisted of total mastectomy with low axillary dissection for noninvasive cancers and modified radical mastectomy for invasive cancers. Pathologic findings of the dominant breast cancer and the contralateral lesion were: bilateral, noninvasive: three patients; invasive, noninvasive: (seven patients), and invasive, invasive: three patients. Although follow-up is short (median of 40 months), 82% of the patients who had clinically occult second-breast cancer remain free of disease. During a previous 8-year period, 37 of 500 primary breast cancer patients (7.4%) developed metachronous (33) or synchronous (4) second-breast primary cancers primarily diagnosed clinically or radiologically. Of these, 35 were invasive and two noninvasive cancers; 41% had nodal metastases. A selected "favorable group," 28 of these patients who were free of disease 3 years after their first cancer, was analyzed. The analysis showed that only 10 (36%) were surviving free of disease at 7 years; 25% were free of disease at 10 years. Although the incidence of clinically-recognized, second-primary breast cancer is relatively low, development of a second invasive cancer severely impairs patient survival. Contralateral biopsy would appear useful to identify patients with early invasive or preinvasive cancer in the second breast, which appears normal after clinical observation or mammography. It provides opportunity to reduce the risk of invasive cancer in that breast, as well as to provide important diagnostic and prognostic information.