Diphenylmethylenes

The diphenylmethylene ketal prepared from a catechol (Ph2CCl2, Pyr, acetone, 12 h) or (Ph2CCl2, neat, 170°, 5 min, 59%) can be cleaved by hydrogenolysis (H2/ Pd-C, THF). It has also been prepared from a 1,2,3-trihydroxybenzene (Ph2CCl2, 160°, 5 min, 80% yield) and cleaved by acidic hydrolysis (HOAc, reflux, 7 h). ... 

Methylene, 287 Pivaldehyde Acetal, 289 Acetonide, 289 Cyclohexylidene. 289 Diphenylmethylene, 289 Ethyl Orthoformate, 290 Diisopropylsilylene Derivative, 290... 

A number of imine derivatives have been prepared as amine protective groups, but most of these have not seen extensive use. The most widely used are the ben-zylidene and diphenylmethylene derivatives. The less used derivatives are listed, for completeness, with their references at the end of this section. For the most part, they are prepared from the aldehyde and the amine by water removal cleavage is effected by acid hydrolysis. 

Chemical Name 4-(diphenylmethylene)-1,1-dimethylpiperidinium methyl sulfate Common Name —... 

Auch in Dibenzofulven-Derivaten wird die semicyclische C=C-Doppelbindung durch Diboran unmittelbar abgesattigt9 in 2-Diphenylmethylen-2H-imidazol kann sie bereits mit Natriumboranat in Athanol gesattigt werden10. 

Benzophenon 3-Oxo-cholestan TiCl.,/Li in Glyme, 2 Stdn. 3-Diphenylmethylen-cho- 82 1... 

N-Diphenylmethylen- 374 N-Diphenylmethylen-O-aminocarbonyl- 612 N-[l,3-Diphenyl-propyl-(2) - 374 N-[l,3-Diphenyl-propyliden-(2)]- 374, 377, 380 N-(4-Halogen-phenyI)- 683 N-Heptyl- 375 N-Heptyl-N-acetyl- 376 N-Heptyliden- 375 N-Hcptyliden-O-acetyl- 376 0-(2-Hydroxy-athyl)-N-athoxycarbonyl- 133 N-(4-Hydroxy-phenyl)- 683 0-(2-Hydroxy-l-phenyl-athyI)-N-athoxycarbonyI-aus 0-(ci-AthoxycarbonyI-benzyl)-N-athoxycar-bonyl-hydroxylamin und Lithiumalanat 133 N-Isopropyl- 682 N-Isopropylidcn- 613 N-Methyl- 133, 682 O-Methyl-N-bcnzyliden- 377 O-Methyl-N-benzyliden- 375 0-Methyl-N-(4-chlor-benzyl)- 375 0-Methyl-N-(4-chlor-benzyliden)- 375 N-Methy -N,0-diacetyI- 682 N-(4-Methyl-phenyl)- 683 0-McthyI-N-( 1 -phenyl-athyliden)- 375 N-(4-Methylthio-phenyl)- 684 N-(4-Nitro-benzyl)- 374 N-[4-Nitro-benzyliden - 374, 377 N-(2-Nitro-phenyl)- 562 N-(4-Nitro-phenyl)- 682 N-Nitroso-N-cyclohexyl- 697 N-Octyl- 374 N-Octyl-(2)-N-acetyl- 376 N-Octyliden- 374 N-0ctyliden-(2)-0-acctyl- 376 N-(Pentafluor-phenyl)-0,N-diacetyl- 697 N-Phenyl- 474, 481, 682, 783 N-Phenylacetyl-O-benzoyl- 265 N-(l-Phenyl-athyl)- 374 N-(l-Phenyl-athyl)-N-acetyl- 376 N-(l-Phenyl-athyliden)-374, 613 N-( l-Phenyl-athyliden)-0-acetyl- 376 N-[ 1 -Phenyl-buten-( 1 )-yl-(3)-iden]- 582 N-f4-Phenyl-butyl-(2)-iden]- 581 N-Phcnyl-N,0-diacetyl- 682 N-(4-Phenylthio-phenyl)- 684 N-Propyl-N-cyclohexyl- 376 N-Propyl-N-isopropyl- 376 O-Sulfonyl- 481 N-(4-Sulfonyl-phenyI)- 683 N-(2-Vinyl-phenyl)- 698... 

DiphenyI-athyI)- -dinitril 559 (1,2-Diphenyl-athyIiden)- -dinitril 559 Diphenylmethyl- -athylester-nitril 581 Diphenylmethylen- -athylester-nitril 206, 581 Dodecanoyl- -diathylester 195 Hexyliden-(2)- -dinitril 666 Hydroximino- -diathylester 6/3 Hydroxy- 314... 

Dimcthyl-5-(dimethylamino-methyl)- 303 5-Diphenylmethylen- 63 5-(a-Hydroxy-benzyliden)-l-benzoyl- 63... 

Diphenylmethylen- 497 2a(S),3a(0)-Dithiocarbonato- 340 22,26-Epimino-3/3-hydroxy-5a- 104 2a,3a-Epithio- 340, 448 4a,5a-Epoxy-6-oxo- 549 Hydroxy- 567 3 -Hydroxy- 75, 731 3/3-Hydroxy- 75, 608, 720, 747 5/3-Hydroxy-3/3-acetoxy-6-hydroximino- 521 3/3-Hydroxy-2a-(athoxy-thiocarbonylthio)- 340 3/3-Hydroxy-7,7-dideutero-5a- 608 3/3-Hydroxy-5a, 6a -epoxy- 423 2/3-Hydroxy-3a -mcrcapto- 102 3a-Hydroxy-2/3-mcrcapto- 102 3/3-Hydroxy-2/3-mercapto- 340 3/3-Hydroxy-7-oxo-5a- 608 4a -Hydroxy-6-oxo-5ct - 549 2/3-Hydroxy-3a-thiocyanato- 102 3a-Hydroxy-2/3-thiocyanato-102... 

EPR studies of diphenylmethylene and a number of other arylmethylenes have indicated that these carbenes have triplet ground states.<30) Photolysis of diphenyldiazomethane in olefin matrices results in the formation of triplet diphenylmethylene, which undergoes primarily abstraction reactions with the olefins. Cyclopropanes are produced as minor products. 

Suitable carbonyl compounds can thus be olefmated photochemicully with (diazobenzyl)diphenylphosphine oxide (7), the oxygen function being substituted by a diphenylmethylene group 18,20). Hence irradiation of 7 for a sufficient length of time in the presence of the corresponding unsaturated ketones affords the hepta-fulvene 27 23), the trans-1,3-butadiene 28 22 and the cross-conjugated hexatriene 2922> by direct olefination with the intermediate 9. 

S/S insertion is also part of the reaction scheme when carbenes (or carbenoids) interact with l,6,6aX,4-trithiapentalenes 377 (Scheme 38) 352). The origin of the 4-diphenylmethylene-thiopyran 378 resulting from the reaction at higher catalyst concentration has not been elucidated, however. 

In the paper published in 1900, he reported that hexaphenylethane (2) existed in an equilibrium mixture with 1. In 1968, the structure of the dimer of 1 was corrected to be l-diphenylmethylene-4-triphenylmethyl-2,5-cyclohexadiene 3, not 2 [38]. Since Gomberg s discovery, a number of stable radicals have been synthesized and characterized, e.g., triarylmethyls, phenoxyls, diphenylpicryl-hydrazyl and its analogs, and nitroxides [39-43]. The radical 1 is stable, if oxygen, iodine, and other materials which react easily with it are absent. Such stable radicals scarcely initiate vinyl polymerization, but they easily combine with reactive (short-lived) propagating radicals to form non-paramagnetic compounds. Thus, these stable radicals have been used as radical scavengers or polymerization inhibitors in radical polymerization. 

DIPHENYLMETHYLENE (DPM) AND ITS DERIVATIVES, DIMESITYL-CARBENE (DMC), DIBENZOCYCLOHEPTADIENYLIDENE (DCH) AND SILA-ANTHRYLIDENE (SA)... 

Diphenylmethylene is certainly the most exhaustively studied of the aromatic carbenes. Low temperature epr spectroscopy (Trozzolo et al., 1962) clearly established the ground state of this carbene as the triplet. The optical spectrum of the triplet was recorded first in a 1,1-diphenylethylene host crystal (Closs et al., 1966) and later in frozen solvents (Trozzolo and Gibbons, 1967). 

Diphenylmethylene was the first carbene to be studied using fast, time-resolved spectroscopic methods (Closs and Rabinow, 1976). Since then both nanosecond and picosecond laser techniques have been used to probe this intermediate (Eisenthal et al., 1980, 1984 Hadel et al., 1984a,b Griller et al., 1984b Langan et al., 1984 Sitzmann et al., 1984). The results of these experiments are essentially undisputed, but the interpretation of them still remains somewhat controversial. 

Reactions of methoxycarbonylformonitrile, furonitrile and substituted benzoni-trile oxides (4-Me, 4-OMe, 3-OMe, 4-C1, 3-C1, 2,4-di-Cl, 4-F as substituents) with dimethyl 7-(diphenylmethylene)bicyclo[2.2. l]hept-2-ene-5,6-dicarboxylate led exclusively to exo cycloadducts 82 (R = C02Me, 2-furyl, substituted phenyl), which, on irradiation with a low-pressure mercury lamp, afforded 3-azabicyclo [4.3.0]nonadiene-7,8-dicarboxylates 83 as the only products. The 1,3-dipolar cycloaddition, followed by a photorearrangement, provides a new method for obtaining tetrahydro-27/ -pyridine derivatives from cyclopentadiene (245). 

Trifluoroborane-etherate was used in this reaction. The same route seems to be quite convenient for the preparation of many other (diphenylmethylene-amino)boranes including dihaloborane derivatives. Similarly, B-monohalo derive atives such as [(C6Hs)2ON—B(C6H5)C1] and B-diaryl derivatives were synthesized by the cited method 47)... 

---