摘要:

AbstractAlkyllithiums undergotransaddition to 3‐(trimethylsilyl)‐2‐propyn‐1‐ols to yield (1‐lithiovinyl)silanes. Due to unidentified side‐reactions, yields do

ISSN:0165-0513    

DOI:10.1002/recl.19851040102

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractCrystals of cyanocyclopropane have been grown from liquid. At −85°C, cell parameters area= 7.244(5),b= 7.821(2), c = 6.916(3) Å in the orthorhombic space groupPnmawithZ= 4. Intensity data were collected in three different ways,viz. photographically using rotation andWeissenbergtechniques and electronically by means of a diffractometer. Within the limits of accuracy, the three data sets result in equal bond lengths and angles. The most important result from the structure determination is the difference of 0.033 Å between the lengths of the distal and vicinal ring bonds, which had not previously been measured directly from X‐ray exper

ISSN:0165-0513    

DOI:10.1002/recl.19851040103

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe shielding effects of the sulfur atom on neighbouring carbons in 36 thioketones have been characterized by13C NMR. The results are compared with those for the carbonyl derivatives. The importance of these data for structural elucidations is discussed.

ISSN:0165-0513    

DOI:10.1002/recl.19851040104

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractA synthesis of 3β‐acetoxy‐2aα,5aβ‐dimethyl‐3,4,5,5a,7,8,8aα,8bα‐octahydro‐2H‐naphtho‐[1,8‐bc]furan‐2,6(2aH)‐dione1is explored starting from 5β‐acetoxy‐1,4aβ‐dimethyl‐4,4a,5,6,7,8‐hexahydronaphthalen‐2(3H)‐one2and methyl 5,5‐(ethylenedioxy)‐2‐oxo‐4aβ‐methyl‐2,3,4,4a,5,6,7,8‐octahydronaphthalene‐1‐carboxylate3. A successful route to lactone1was found via methylation and reduction of oxo ester3to methyl 5‐oxo‐2β‐acetoxy‐1α,4aβ‐dimethyl‐1,2,3,4,4a,5,6,7,8,8aα‐decahydronaphthalene‐1β‐carboxylate5. Transformation of5into 5‐oxo‐2β‐acetoxy‐6‐bromo‐1α,4aβ‐dimethyl‐1,2,3,4,4a,5,

ISSN:0165-0513    

DOI:10.1002/recl.19851040105

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe photoisomerization of a series of (highly) crowded α‐oxo oxime ethers (3–8) has been studied under conditions of direct irradiation (λ 300 and 350 nm) and of triplet photosensitization. The decay ratiosk5/k6for the two conditions are the same for a given compound, illustrating that the isomerization of the α‐oxo oxime ethers, upon direct irradiation, also proceeds from the (lowest) excited triplet state. The excited singlet and triplet state energies are reported, as well as ΔG0(E)‐ΔG0(Z) for4(‐ 8.2 ± 0.5) and6(7.7 ± 0.5 kJ·mol−1), determined by thermal equilibration with I2at 353 K. The decay ratiok5/k6is significantly smaller for4and5than for3and6‐8due to steric hindrance upon relaxation of the perpendicular ground state to t

ISSN:0165-0513    

DOI:10.1002/recl.19851040106

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe protonation and sulfonation of a series of azulenes (1–9) has been studied. The protonations occur at the 1‐ and 3‐positions, and with6at the formyl oxygen. Reaction of9in CF3CO22H leads to a preferred deuteration of the 3‐ as compared with the 1‐postion (k1/k30.64) which is ascribed to relief of steric strain between the 3‐ and 4‐substituents on deuteration at C(3).Reaction of the azulenes with SO3in (2H8)dioxane or (2H3)nitromethane leads to sulfodeprotonation at the 1‐ and/or 3‐position and, if these positions are blocked bytert‐butyl groups, to sulfodeprotonation at the less reactive 5‐ and 7‐positions in accordance with predictions based on localization energies. Reaction of2and3in 105.1% H2SO4leads to sulfonation of the respective corresponding 1‐ and 3‐azulenium ions with formation of the 2‐sulfonic acids, whereas reaction of7in 98.4% H2SO4leads to sulfonation of its 1‐azulenium ion at thepara‐position of the 2‐ or 3‐phenyl group.Reaction of2, 3and9with SO3in (2H3)nitromethane leads to the formation of the stable sulfonation σ‐complexes10 + 11, 14 + 16 + 17and20, respectively. The relatively high stability of the σ‐complexes is due to the high rate of addition of SO3to the azulenes at the 1‐ and 3‐positions, combined with the very low rate of proton transfer of theC(sp3)‐bonded hydrogen of the reaction centre caused by the largeperi‐strain that results on bringing the sulfo group into the plane of the azulene skeleton.Addition of 1,3‐dimethoxybenzene to the mixtures formed from both2and3with 2 or 3 equivalents of SO3in nitromethane leads to sulfonation of the added substrate. The trans‐sulfonating species derived from2are11and13(of which the

ISSN:0165-0513    

DOI:10.1002/recl.19851040107

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19851040101

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY