ISSN:
0947-3440
Keywords:
Phospha ene reaction
;
Phosphaalkynes
;
Phosphaalkenes
;
Alkylidenecyclopropanes
;
Allenes
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Phosphaalkynes readily participate in ene reactions both with alkylidenecyclopropanes and with allenes to furnish phosphaalkenes (the products of a simple ene reaction) and phosphanes (the products of a tandem ene reaction). Thus, irrespective of the stoichiometry, the thermal reactions of the phosphaalkynes 1a-c with isopropylidenecyclopropane (8) or cyclopropylidenecyclopentane (11) proceed by a tandem ene process with retention of the three-membered ring unit to furnish the corresponding bis(cyclopropyl)phosphanes 10a-c or 12. In contrast, with cyclopropylidenecyclohexane (13) as the H-donor, the specific formation of either the monoadducts 14a,c or of the bisadducts 15a,c can be controlled. A crystal structure analysis of 15a confirmed the structures of the tandem ene products while the constitutions and configurations of the novel P-cyclopropylphosphaalkenes 14a,c were unequivocally elucidated by an X-ray crystal structure analysis of the corresponding, W(CO)5-complexed system 16. Alkylated allenes such as 1,1-dimethylallene (17), vinylidenecyclohexane (20), tetramethylallene (22), or 1,2-cyclononadiene (24) undergo thermal addition by way of a double ene process to afford the phosphaalkynes 1. In each case, regiospecific attack of the phosphorus atom at the central C-atom of the cumulene system results in the formation of the structurally unique phosphanes 21, 23a,b, and 25a,b. On the other hand, thermal reactions of 1a,b in the presence of 1,1-diethylallene (26) come to a standstill after the first ene addition and furnish the cross-conjugated phosphatrienes 27a,b as the first representatives of the previously unknown phospha[3]dendralene system. The thermally initiated tandem ene reactions of the phosphaalkynes 1 with propadiene (28) or tert-butylallene (30) each proceed through transfer of a vinylic hydrogen atom from the ene to the enophile to afford the bis(propargyl)phosphanes 29a,b and 31, respectively, as addition products.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199719970906
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