Facile Synthesis of Heteroalkenes CF₃ECF₂ (EP, As)

Abstract

A general entry to E  C(p‐p)π systems might be afforded by the elimination of Me3SnF from stannylated trifluoromethylelement compounds. Thus, the phosphane 1a (E  P) and the arsane 1b (E  As) react in the gas phase at 10−3 torr and 300—340oC to give the heteroalkenes 2a and 2b, respectively, in quantitative yield. CF3As  CF2 is the smallest molecule known so far with As  C bonding.—Further examples of species thus generated are S  CF2, Se  CF2, and Me3SnP  CF2.

Scope and Limitations of the Base-Catalyzed Phospha-Peterson PC Bond-Forming Reaction

“…The molecular structure of the 1,2-diphosphetane ( 3a ), formed from the dimerization of 2a , was confirmed using X-ray crystallography (Figure ). The [2+2] cycloaddition of phosphaalkenes is often observed when insufficient thermodynamic and/or kinetic stability is conferred to the PC bond, although formally, the dimerization is symmetry forbidden. 1h,1m,,,− Phosphaalkenes have been observed to dimerize with both head-to-tail (to 1,3-diphosphetanes) and head-to-head (to 1,2-diphosphetanes) regiochemistry, with head-to-tail cycloaddition being most common. However, it has been proposed that phosphaalkenes bearing larger P than C substituents will favor head-to-head dimerization, because the long P−P bonds and short C−C bonds in the 1,2-diphosphetane will reduce intramolecular steric repulsions better than in a 1,3-diphosphetane containing four intermediate-length P−C bonds .…”

Stable C-Halogenated Arsaalkenes

“…Arsaalkenes halogenated at the alkene carbon atom should be of great interest as synthons for the preparation of functionalized arsaalkenes via halogen−metal exchange with n -butyllithium. The first representative of this new class of arsaalkenes to be isolated was F 3 CAsC(F)NR 2 ,2h whereas F 3 CAsCF 2 was characterized only as a transient species. However, due to the high kinetic stability of the CF bond, functionalization is not easy in this case.…”

PhP=CPh2 and Related Phosphaalkenes: A Solution Equilibrium between a Phosphaalkene and a 1,2‐Diphosphetane

“…In the absence of a crystal structure, this compound had previously been assigned as the 1,3‐diphosphetane . The regioselective [2+2] cyclodimerization of phosphaalkenes is well‐established, and affords either the head‐to‐tail (i.e., 1,3‐diphosphetane) or the head‐to‐head product (i.e., 1,2‐diphosphetane) , , . Dimer 2a was fully characterized by using 31 P, 1 H and 13 C{ 1 H} NMR spectroscopy, mass spectrometry and elemental analysis.…”