Selective Enzymatic Oxidation of Silanes to Silanols

Compared to the biological world's rich chemistry for functionalizing carbon, enzymatic transformations of the heavier homologue silicon are rare. We report that a wild‐type cytochrome P450 monooxygenase (P450_(BM3) from Bacillus megaterium, CYP102A1) has promiscuous activity for oxidation of hydrosilanes to give silanols. Directed evolution was applied to enhance this non‐native activity and create a highly efficient catalyst for selective silane oxidation under mild conditions with oxygen as the terminal oxidant. The evolved enzyme leaves C−H bonds present in the silane substrates untouched, and this biotransformation does not lead to disiloxane formation, a common problem in silanol syntheses. Computational studies reveal that catalysis proceeds through hydrogen atom abstraction followed by radical rebound, as observed in the native C−H hydroxylation mechanism of the P450 enzyme. This enzymatic silane oxidation extends nature's impressive catalytic repertoire

Selective Enzymatic Oxidation of Silanes to Silanols

Compared to the biological world's rich chemistry for functionalizing carbon, enzymatic transformations of the heavier homologue silicon are rare. We report that a wild‐type cytochrome P450 monooxygenase (P450_(BM3) from Bacillus megaterium, CYP102A1) has promiscuous activity for oxidation of hydrosilanes to give silanols. Directed evolution was applied to enhance this non‐native activity and create a highly efficient catalyst for selective silane oxidation under mild conditions with oxygen as the terminal oxidant. The evolved enzyme leaves C−H bonds present in the silane substrates untouched, and this biotransformation does not lead to disiloxane formation, a common problem in silanol syntheses. Computational studies reveal that catalysis proceeds through hydrogen atom abstraction followed by radical rebound, as observed in the native C−H hydroxylation mechanism of the P450 enzyme. This enzymatic silane oxidation extends nature's impressive catalytic repertoire

Political travel across the ‘Iron Curtain’ and Communist youth identities in West Germany and Greece in the 1970s and 1980s

This article explores tours through the Iron Curtain arranged by West German and Greek pro-Soviet Communist youth groups, in an attempt to shed light on the transformation of European youth cultures beyond the ‘Americanisation’ story. It argues that the concept of the ‘black box’, employed by Rob Kroes to describe the influence of American cultural patterns on Western European youth, also applies to the reception of Eastern Bloc policies and norms by the Communists under study. Such selective reception was part of these groups’ efforts to devise a modernity alternative to the ‘capitalist’ one, an alternative modernity which tours across the Iron Curtain would help establish. Nevertheless, the organisers did not wish such travel to help eliminate American/Western influences on youth lifestyles entirely: the article analyses the excursions’ aims with regard to two core components of youth lifestyles in Western Europe since the 1960s, which have been affected by intra-Western flows, the spirit of ‘doing one’s own thing’ and transformations of sexual practices. The article also addresses the experience of the travellers in question, showing that they felt an unresolved tension: the tours neither served as a means of Sovietisation nor as an impulse to develop an openly anti-Soviet stance.PostprintPeer reviewe

Synthesis of SiCl₄ via the Chloride Salt-Catalyzed Reaction of Orthosilicates with SOCl₂

This paper details a method to chlorinate tetraalkyl orthosilicates in the presence of a catalyst using SOCl₂ as the chloride source/deoxygenating agent. Several inexpensive catalysts were screened, and it was found that soluble chloride salts performed better than Lewis base catalysts. The optimized reaction employed a widely used and commercially available soluble chloride salt catalyst (e.g., NBu₄Cl, 0.4 equiv), 16 equiv of SOCl₂, and afforded quantitative yield of SiCl₄ after 3 h. As the bulk of the orthosilicate substrate increased, the yield of SiCl₄ decreased. A reaction mechanism has been proposed

Synthesis of SiCl₄ via the Chloride Salt-Catalyzed Reaction of Orthosilicates with SOCl₂

This paper details a method to chlorinate tetraalkyl orthosilicates in the presence of a catalyst using SOCl₂ as the chloride source/deoxygenating agent. Several inexpensive catalysts were screened, and it was found that soluble chloride salts performed better than Lewis base catalysts. The optimized reaction employed a widely used and commercially available soluble chloride salt catalyst (e.g., NBu₄Cl, 0.4 equiv), 16 equiv of SOCl₂, and afforded quantitative yield of SiCl₄ after 3 h. As the bulk of the orthosilicate substrate increased, the yield of SiCl₄ decreased. A reaction mechanism has been proposed

Selective Enzymatic Oxidation of Silanes to Silanols

Compared to the biological world’s rich chemistry for functionalizing carbon, enzymatic transformations of the heavier homologue silicon are rare. We report that a wild-type cytochrome P450 monooxygenase (P450BM3 from Bacillus megaterium, CYP102A1) has promiscuous activity for oxidation of hydrosilanes to make silanols. Directed evolution enhanced this non-native activity and created a highly efficient catalyst for selective silane oxidation under mild conditions with oxygen as terminal oxidant. The evolved enzyme does not touch C–H bonds also present in the silane substrates, nor does this biotransformation lead to disiloxane formation, a common problem in silanol syntheses. Computational studies reveal that catalysis proceeds through hydrogen atom abstraction followed by radical rebound, as observed in the P450’s native C–H hydroxylation mechanism. Enzymatic silane oxidation now extends Nature’s already impressive catalytic repertoire