摘要:

AbstractX‐ray crystal structure determinations of tetramesityldisilene (1) at 295 K, where it is bright orange, and at 173 K, where it is pale yellow, were experimentally equivalent. The thermochromism of1, therefore, is not due to changes in conformation; a vibrational origin is considered. The crystal structure of unsolvated1differs substantially from that of the toluene solvate (1·C7H8) because of different crystal packing of the two forms. These two solid‐state structures are compared with those of four other disil

ISSN:1042-7163    

DOI:10.1002/hc.520010102

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe rate of alkylation of (2‐N,N‐dimethylaminophenyl)diphenylphosphine with benzyl bromide in chloroform is faster than that of the corresponding reaction of (4‐N,N‐dimethylaminophenyl)diphenylphosphine. This result is discussed in terms of a through‐space N2p–P(IV) interaction for the former.The rate of alkaline cleavage of benzyl(4‐N,N‐dimethylaminophenyl)diphenylphosphonium bromide, which gives toluene, is slower than the rate of alkaline cleavage of benzyl(2‐N,N‐dimethylaminophenyl)diphenylphosphonium bromide, which gives dimethylaniline. This result is also discussed in terms of the through‐space N2p–P(IV) interaction.The31P NMR spectra of a series ofortho‐dimethylamino‐substituted triarylphosphines and benzyltriarylphosphonium halides show that the phosphorus atom is more shielded than in the correspondingpara‐dimethylamino compounds, as anticipated on the basis of an N2p–P

ISSN:1042-7163    

DOI:10.1002/hc.520010103

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

Abstract1‐(Trimethylsilylmethyl)benzotriazole is readily prepared from benzotriazole and chloromethyltrimethylsilane. It undergoes fluoride‐catalyzed desilylation with carbonyl compounds and forms an anion that can be alkylated and acylated readily and undergoes Peterson olefination. 1‐(Cyclohexylidenemethyl)benzotriazole is lithiated exclusively at the α carbon atom, and the anion can be cleanly alkylated.1‐(α‐Acylalkyl)benzotriazoles are reduced to ketones with zinc and acid. The stability of 1‐alkenylbenzotriazoles to hydrolysis has

ISSN:1042-7163    

DOI:10.1002/hc.520010104

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractSulfur and selenium react with a 1,2‐dihydrophosphete P‐W(CO)5complex at ca. 120°C to give the corresponding 2,5‐dihydro‐1,2‐thiaphosphole and 2,5‐dihydro‐1,2‐selenaphosphole complexes, respectively. These products result from an insertion of S or Se into the PCsp3bond of the

ISSN:1042-7163    

DOI:10.1002/hc.520010105

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe reaction of 4,5‐dimethyl‐2‐phenylphosphinine with sulfur in boiling benzene in the presence of N‐methylimidazole as a catalyst first yields a P‐sulfide. This monosulfide further reacts with sulfur to give a diphosphinine trisulfide and a diphosphinine tetrasulfide. The X‐ray crystal structure analysis of the trisulfide has been carried out.The two head‐to‐tail 1,6‐dihydrophosphinine rings are connected by PSC and PC links, thus forming a central 1,2,4‐thiadiphospholane heterocycle. The PC bridge is weak [1.881(3) Å] and sulfur can insert into it to give the symmetrical tetrasu

ISSN:1042-7163    

DOI:10.1002/hc.520010106

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractTellurium dioxide, trimethylchorosilane, acetyl chloride, or acetyl bromide in glacial acetic acid generated a homogeneous solution. Addition of cyclohexene producedtrans‐2‐halocyclohexyl tellurium trihalides of excellent purity in 70% yield. With dichloromethane or ethanol‐free chloroform the same compounds were obtained from heterogeneous reaction mixtures.trans‐2‐Methoxycyclohexyl tellurium trichloride was obtained quantitatively from tellurium dioxide, trimethylchlorosilane, and cyclohexene in absolute methanol. In the absence of cyclohexene, tellurium tetrachloride was obtained in 91% yield from tellurium dioxide and trimethylchlorosilane in chloroform, and tellurium tetrabromide in 98% yield from tellurium dioxide and acetyl bromide in glacial ac

ISSN:1042-7163    

DOI:10.1002/hc.520010107

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractTributylstibine can mediate the olefination of carbonyl compounds with bromomalonic ester and with dibromomalonic ester. An initial halophilic attack of tributylstibine on the bromine of bromomalonic or dibromomalonic ester forming an ion pair of bromotributylstibonium cation and malonic(A)or bromomalonic ester carbanion(B), respectively, is proposed. These ion pairs react with carbonyl compounds to achieve subsequent olefination. Alternatively, 2 equiv ofAcollapse, with elimination of malonic ester, to form stiboraneD, and the ion pairBreacts with another equivalent of tributylstibine to form stiboraneD.This last undergoes a Wittig‐type reaction with carbonyl compound to achieve olefinatio

ISSN:1042-7163    

DOI:10.1002/hc.520010108

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA set of mutually compatible torsional, stretch, and bending parameters have been devised that reproduce with considerable accuracy the calculated structures of simple silenes and disilenes, and the crystal structure data available for solid silenes and disilenes.

ISSN:1042-7163    

DOI:10.1002/hc.520010109

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractReaction of pinanediol boronates with (1,1‐dichloroethyl)lithium generated in situ at −78°C followed by rearrangement of the resulting borate complex2Sin the presence of zinc chloride at 25°C has resulted in chirally biased insertion of the 1‐chloroethyl group into the carbon–boron bond. (s)‐Pinanediol phenylboronate (7) produced (s)‐pinanediol (1S)‐(1‐chloro‐1‐phenylethyl)boronate (8S) in 92% DE. Nonstererospecific reaction with ethylmagnesium bromide to form (s)‐pinanediol (1S)‐(1‐phenyl‐1‐methylpropyl)boronate (5S) reduced the DE to 88%. Peroxidic deboronation yielded (R)‐(+)‐2‐phenyl‐2‐butanol (6R) (84% EE). (s)‐Pinanediol ethylboronate (4) with (1,1‐dichloroethyl)lithium showed the opposite chiral preference, yielding (s)‐pinanediol (1R)‐(1‐chloro‐1‐methylpropyl)boronate (3R) (89% DE), which was converted by phenylmagnesium bromide followed by hydrogen peroxide to6R(76% EE). Diastereoselections were small in reactions of (1,1‐dichloroethyl)‐lithium withn‐alkylboronates9aand13and with cyclohexylboronate9c. The13was converted to the enantiomer of the insect pheromone frontalin (17) (21% EE). Good diastereoselections were found with α‐substituted alkylboronates9band18, but the configurations of the products could not be determined. (s)‐Pinanediol (1,1‐dichloroethyl)boronate (1) reacts with Grignard rea

ISSN:1042-7163    

DOI:10.1002/hc.520010110

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY

摘要:

Abstract2,4‐Dienals were synthesized conveniently by using a new formylenylolefination method. The aldehydes were reacted with formylallyltriphenylarsonium bromide (2) in Et2OTHFH2O (9 : 1 : 0.05) in the presence of K2CO3at room temperature to give (2E,4E)‐and (2E,4Z)‐dienals, in favor of the former. They could be easily separated by chromatography, and the latter, in CH2Cl2, could be converted to the former on treatment with a catalytic amount of iodine in daylight. The configurations of the (E,E) products have been conveniently identified by1H NMR determined in C6D6. The syntheses of two natural products, navenone A andOtanthus maritimaamide, by this method are also reported

ISSN:1042-7163    

DOI:10.1002/hc.520010111

出版商:VCH Publishers, Inc.    

年代:1990

数据来源: WILEY