摘要:

Abstract1‐(2,4,6‐Tri‐t‐butylphenyl)‐1‐phosphaallene reacted with dichlorocarbene to give 2‐dichloromethylene‐1‐(2,4,6‐tri‐t‐butylphenyl)‐1‐phosphirane. The structure was confirmed by X‐ray crystal structure analysis. A similar isomerization product was obtained in the reaction of dichlorocarbene with 3‐phenyl‐1‐(2,4,6

ISSN:1042-7163    

DOI:10.1002/hc.520050302

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractNucleophilic cleavage by potassium t‐butoxide on hexaphenyl digermanes, distannanes, and diplumbanes, in N,N′‐dimethylpropyleneurea (DMPU) solvent, provides a facile method for preparation of triphenyl germyl, stannyl, and plumbyl a

ISSN:1042-7163    

DOI:10.1002/hc.520050303

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe addition of n equiv of MesNHLi (n = 1, 2, 3, 4) and m equiv of 12‐crown‐4 (m = 0.1, 1, 2, 3, 4) to (RsiCl2)2(R = Mesityl; t‐Butyl) in THF at −78°C resulted in higher yields and improved selectivities of cyclodisilazanes and azadisilacyclopropanes. The reaction of 2 equiv of MesNDLi with (MesSiCl2)2(I) yielded cis‐2‐chloro‐1,2,3,4‐tetramestylcyclodisilazane (2a) with 95% SiH deuteration.2awas quantitatively chlorinated with retention of stereochemistry by N‐chlorosuccinimide to give the cis dichlorocyclodisilazane (3). Variable‐temperature1H NMR studies from −70°C to 25°C in d8‐THF were performed on1,2a,2b, and3.1exhibited little variation throughout the temperature range, whereas2a,2b, and3showed several rotational isomers. trans‐2,3‐Bis(mesitylamino)‐1,2,3‐trimesitylazadisilacyclopropane was shown to isomerize to the cis isomer in the presence of n‐BuLi or MesNHLi. The molecular structures of1and3were determined by X‐ray crystallography. Compound1crystallized in the monoclinic space group P21/c, with cell parameters a = 16.599(2) Å b = 14.633(2) Å, c = 16.945(2) Å, β = 92.044(13)°, V = 4113.1(8) Å3, Z = 8, d (calcd) = 1.409 g/cm3, and R = 6.88%. Compound 3 ° C6H6crystallized in the orthorhombic space group Pbca, with cell parameters a = 17.906(4) Å, b = 13.918(3) Å, c = 31.700(6) Å, V = 7900(3)

ISSN:1042-7163    

DOI:10.1002/hc.520050304

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractReaction of Ph2Si(NHNHMe)2(1) with n‐BuLi and Ph2SiCl2in 1 : 2 : 1 ratio afforded 54% of 1,2,4‐triaza‐1‐methyl‐4‐methylamino‐3,3, 5, 5‐tetraphenyl‐3,5‐disilacylopentane (2). In the presence of a catalytic amount of n‐BuLi,2is rearranged to two isomers, 1,2,4,5‐tetraaza‐1,4‐dimethyl‐3,3,6,6‐tetraphenyl‐3,6‐disilacyclohexane (3) and 1,2,4,5‐tetraaza‐1,5‐dimethyl‐3,3,6,6‐tetraphenyl‐3,6‐disilacyclohexane (4), with3as the major product. The crystal structure of3reveals a twist‐boat conformation of the Si2N4ring [a = 10.691(4) Å, b = 13.178(4) Å, c = 17.812(3) Å, β = 95.11(7)°; monoclinic, P21/n; Z = 4], in which eachN(Me)N(H)

ISSN:1042-7163    

DOI:10.1002/hc.520050305

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

Abstract2‐Pyridyl 2‐thienyl sulfoxide was found to react with variously substituted 2‐thienyllithiums and 2‐selenophenyllithium, exclusively affording 2‐(2‐pyridyl)thiophenes and 2‐(2‐pyridyl)‐selenophene and the disulfides derived from the substituted thiophenes and selenophene. Apparently, ligand exchange precedes ligand coupling. The coupling product always involved the pyridine nucleus, but no bithienyl‐type p

ISSN:1042-7163    

DOI:10.1002/hc.520050306

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractHeteroarylthiomethyltrimethylsilanes bearing a 2‐pyridyl, 2‐imidazolyl, 5‐tetrazolyl, or 2‐pyrimidinyl group, readily prepared by the reaction of heteroarylmercaptans with halomethyltrimethylsilane in the presence of a base, are synthetic equivalents of heteroarylthiomethyl anions, otherwise inaccessible, and are effective reagents for the introduction of a heteroarythiomethyl group at a carbonyl carbon atom in the presence of a catalytic amount of tetrabutylammonium f

ISSN:1042-7163    

DOI:10.1002/hc.520050307

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe bisketenes 2‐phenyl and 2‐methyl‐3‐(trimethylsilyl)‐1,3‐butadiene‐1,4‐dione (8and10) are calculated on the basis of additivity of substituent effects to be less stable than the 3‐phenyl and 3‐methyl‐4‐(trimethylsilyl)cyclobut‐3‐ene‐1,2‐diones (7and9) by 1.9 and 2.6 kcal/mol, respectively. In agreement with this prediction,8and10are formed by photolysis of7and9, respectively, and undergo thermal reversion to their precursors at similar rates. The concentration of8in thermal equilibrium with7in CDCl3, as measured by1H NMR spectroscopy, varied from 2.8% (161°C) to 0.5% (100.5°C), whereas the amount of10present at equilibrium with9was distinctly less. These measurements allowed the calculation of values ofΔG° (25°C) = 4.4 kcal/mol,ΔH° = 6.9±(1.3) kcal/mol, andΔS° = 8.5 (±3.2) cal/deg mol for the conversion of7to8, and the equilibrium concentration of8at 25°C was estimated to be 0.06%. The triisopropylsilyl analog12of8was prepared and at 66°C was 2.6 times more reactive in ring closure to the corresponding cyclobutenone compared to8. Reactions of8and10with MeOH in CDCl3give the isolable monoketenes 3‐phenyl and 3‐methyl‐2‐(trimethylsilyl)‐3‐carbomethoxy‐1‐ene‐1‐one (20,21). Reaction of20with excess MeOH or H2O gave the diastereomeric dimethyl 2‐(trimethylsilyl)‐3‐phenylsuccinates (22) or ester‐acids24,

ISSN:1042-7163    

DOI:10.1002/hc.520050308

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractTreatment with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) oxidized 2,6‐diethyl‐1,3,5,7,8‐pentamethylpyrromethene–BF2complex1, 13,14‐trimethyl‐2, 3, 4, 5,9,10,11,12‐octahydroindomethene–BF2complex5, and 1,3,5,7,8‐pentamethyl‐1,2,3,5,6,7‐hexahydropyromethene–BF2complex8to the weakly fluorescent 3‐formyl, 5‐oxo, and 8‐formyl derivatives4,6, and9, respectively. The dye1was oxidized by lead tetraacetate to 1,7,8‐trimethyl‐2,6‐diethyl‐3,5‐diacetoxymethylpyrromethene–BF2complex12[λf(ethanol) 538 nm, Φ 0.62, λlas(ethanol) 555–570 nm]. Catalytic reduction (Pd/C) converted the aldehyde4to 2,6‐diethyl‐3‐hydroxymethyl‐1,5,7,8‐tetramethylpyrromethene

ISSN:1042-7163    

DOI:10.1002/hc.520050309

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe generality of the intramolecular cyclization of suitable nucleophilic sites to a S+CH2center created by a sila‐Pummerer rearrangement has been investigated. Successful nucleophilic sites included the OH group (in alcohols, carboxylic acids, and hydroxylamines) and the NH group (in amines and carbamates): attempts to produce carbon‐based nucleophilic sites were not effective. Successful cyclizations were achieved to produce sulfur heterocycles with 5‐, 6‐, and 7‐m

ISSN:1042-7163    

DOI:10.1002/hc.520050310

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractReactions of (Me3Si)2NPNsiMe3with chloroalkanols, N‐methylpropargylamine, 3‐butyne‐2‐one, sucinimide, and chloroacetic acid were investigated. The first step in the reaction is always an addition of the nucleophilic part of the reagent (OH or NH) to the P‐atom. The second step in the reaction, migration of the proton to phosphorus, depends on the substituents on the phosphorus. Highly electronegative substituents increase the stabilization of the P(III) fi

ISSN:1042-7163    

DOI:10.1002/hc.520050311

出版商:VCH Publishers, Inc.    

年代:1994

数据来源: WILEY