Photochemistry of Substituted Benzyldiphenylphosphine Oxides

Zhao, Ningning; Neckers, Douglas C.

doi:10.1021/jo991761r

Cited by 12 publications

(2 citation statements)

References 43 publications

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“…Formation of unidentified products of coupling of the radical pair by attack of the phosphinoyl radical at the ring carbons of the naphthyl ring may occur. Indeed, a recent paper reports the coupling at the ortho and para carbons as well as the benzylic carbon for the radical pair [Ph 2 P(O) • • CH 2 Ph] that is formed photolytically from Ph 2 P(O)CH 2 Ph. The formation of side products and the trapping of radical diffusion products by benzene solvent on photolysis of 1 (Ar = Ph) was discussed in an earlier paper .…”

Section: Discussionmentioning

confidence: 99%

Photo-Arbuzov Rearrangements of 1-Arylethyl Phosphites: Stereochemical Studies and the Question of Radical-Pair Intermediates

Bhanthumnavin

Bentrude

2001

J. Org. Chem.

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The direct UV irradiation of the 1-arylethyl phosphites 7, 8, and 9 was carried out in acetonitrile, benzene, and cyclohexane, as was the triphenylene-sensitized reaction of 9. Dimethyl 1-phenylethyl phosphite, 7, gives the photo-Arbuzov rearrangement product, dimethyl 1-phenylethylphosphonate (10), in 67% average yield and minor amounts (2%) of 2,3-diphenylbutane (11a) in quantum yields of 0.32 and 0.02, respectively. The photorearrangement of optically active, predominantly (R)-1-phenylethyl phosphite 7 (R/S = 97/3; 94% ee), at 35-40 degrees C proceeds with a high degree of stereospecificity at the stereogenic migratory carbon to give predominantly (R)-10 (R/S = 86/14, 72 +/- 2% ee). Use of the nitroxide radical trap TEMPO affords phosphonate 10, presumably all cage product, from predominantly (R)-7 (R/S = 97/3; 94% ee) in 64% yield (80% ee, R/S = 90/10). By contrast, the 1-(4-acetylphenyl)-ethyl phosphite, predominantly (S)-8 (S/R = 98/2, 96% ee), on direct irradiation gives the corresponding phosphonate (12) in only 20% yield along with dimer 11b in 40% accountability yield. Phosphonate 12 is nearly racemic (R/S = 52/48). Direct irradiation of predominantly (R)-9 (R/S = 98/2, 96% ee), a 1-(1-naphthyl)ethyl phosphite, results in a product distribution similar to that from predominantly (R)-7, but with a somewhat higher degree of retention of configuration in the product phosphonate 13 (R/S = 93/7, 86 +/- 3 ee). By contrast, the triplet triphenylene-sensitized photorearrangement of largely (R)-9 (R/S = 98/2, 96% ee) leads to product distributions similar to those from direct irradiation of predominantly (S)-8 and is accompanied by almost total loss of stereochemistry in its product phosphonate, 13 (R/S = 51/49). The partial loss of stereochemistry on direct irradiation of 7 and 9 provides evidence for radical pair formation. Furthermore, these stereochemical results are diagnostic of the multiplicity of the initial radical pair formed. Values for kcomb/krot for the proximate free radical pairs from 7 and 9, derived experimentally, are severalfold larger than those for the proximate singlet pair from Ph2C=C=N-CHPhMe, corrected to 35 degrees C. The possibility that kcomb is increased for the pairs from 7 and 9 is proposed.

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Section: Discussionmentioning

confidence: 99%

Photo-Arbuzov Rearrangements of 1-Arylethyl Phosphites: Stereochemical Studies and the Question of Radical-Pair Intermediates

Bhanthumnavin

Bentrude

2001

J. Org. Chem.

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“…Zhao and Neckers studied the photochemistry of benzyldiphenylphosphine oxides and found that the photochemistry proceeds via the singlet excited state to yield products from both solvent cage and cage escape processes. 46 The radicals obtained from cleavage of the excited state species were both observed by nanosecond laser flash photolysis (Scheme 4.10). The photochemistry is being investigated in terms of its application to photoinitiation and protecting group chemistry.…”

Section: Scheme 318mentioning

confidence: 99%

7 Reaction mechanisms. Part (iv) Radical and radical ion reactions

Donkers

Stringle

Workentin

2001

Annu. Rep. Prog. Chem., Sect. B

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Applications of Diphosphines in Radical Reactions

Kawaguchi

2019

Asian J Org Chem

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Recently, the importance of organophosphorus compounds in organic chemistry has increased. Diphosphines are an attractive source of phosphorus containing two phosphorus groups, which can theoretically be introduced into a carbon framework with high atom economy. There are several diphosphine derivatives, which are closely related to diphosphines, but their reactivities are completely different. In this Minireview, we describe various phosphination reactions with diphosphines and their derivatives under radical conditions.

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Photochemistry of Substituted Benzyldiphenylphosphine Oxides

Cited by 12 publications

References 43 publications

Photo-Arbuzov Rearrangements of 1-Arylethyl Phosphites: Stereochemical Studies and the Question of Radical-Pair Intermediates

Photo-Arbuzov Rearrangements of 1-Arylethyl Phosphites: Stereochemical Studies and the Question of Radical-Pair Intermediates

7 Reaction mechanisms. Part (iv) Radical and radical ion reactions

Applications of Diphosphines in Radical Reactions

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